Well, I guess I can squeeze out some ideas now. Will probably still have more to add later. Just to note, though, this isn't my idea of "the perfect Suikoden," but simply things I want to see as new or returning features.
HeadquartersCustomization: As I said before, I would love to be able to customize your castle, in the sense of selecting where to place the shops and such. I'm sure this would probably have a huge impact on the loading times around the castle, but personally, I wouldn't mind, if they're not much worse than Suikoden V's. If it's for the sake of a well-done castle customization, I'd gladly pay that price. It's really a hassle sometimes, when you have to run, like, 3-5 screens away just to buy some new armor or sleep/save, so being able to pick where you want your shops and whatnot could really help there. Plus, of course, the simple concept of the customization is great to have as an extra, and as others have said, it adds a sort of uniqueness to each player's experience around the HQ. I imagine something along the lines of
Dark Cloud's town-building system would be swell.
Growth: I, too, really liked the gradual "growth" of the headquarters in games like Suikoden II. I liked watching even the town sprite on the world map grow as you progressed.

The upgrades in Suikoden V were somewhat lame, since there were only 2-3, and the slow camera pan was just kind of annoying, really. Of course, I loved exploring the expansions afterwards, but I just preferred the frequency of expansions in some of the previous titles.
On a somewhat related note, I'd like to have a headquarters more like in Suikoden II and III. North Window and Budehuc had more of a town-y feel to them, rather than simply a big castle. I really loved the feeling of running your own whole town/city, and the idea made things seem much more open than just a castle (or colossal ship, in IV's case).
Interactivity: Like Pes said, more interactivity would be great to have. Even if it's just something little like the watchtower from Suikoden II. The decorations that were introduced in Suikoden III were great, though I would love to see more of that in a larger-scale headquarters. Suikoden V had a few things, though not nearly enough, IMO.
- I really like the statue idea from Suikoden II, and was really glad to see that Suikoden V brought it back, and even added two more, for best healer and most damage dealt. ...Though the statues were in a really odd place in Suikoden V. If you didn't explore the lowest floor much, you probably wouldn't even know they were there. That sort of thing should be, like, in the strategy room or something, if you ask me. Somewhere you'll be able to see them often, without going out of your way to do so. The statues are a must-return feature for me. In fact, I'd like to see one or two more, if possible.
- Y'know what, let's just go
Smash Bros.-style and get a whole set of "trophies" while we're at it! That would be great, and would add a ton of extras value. Being able to choose where to put them on display would add to the interactivity of the castle, as well. If you ask me, trophies are simply an awesome idea for Suikoden. Give us something special for completing a mini-game in record time, or hey, for collecting all 108 Stars of Destiny. (Having a full tablet to view is nice, but I think a specialized trophy to represent your accomplishment would be even better.)
Mini-games:- IRON CHEF. Bring it back.
Now. I've gone over this so many times before, but it was just such an awesome idea. It was fun to play around with, and gave you so much more of a reason to collect recipes (as well as the condiments). Not to mention aiming to actually
earn some of the better recipes. A lot of those were actually pretty useful in battle. (It was also hilarious having some that resulted in Fire magic being used in battle. XD)
Really, that's the only specific one I want to return. I actually enjoyed pretty much all of the mini-games in Suikoden II. The Whack-a-Mole game at the farm was pretty intense, and a good excuse to give you the Mole equipment set. The rope-climbing game was simple, but fun for what it was, and some of the rewards were great. (Only way that you could collect any of the Unite-support accessories, I believe.) The fishing was okay, though Suikoden V did a nice job with improving it, I think. ...Well, okay, let's add this one, too:
- Chinchirorin. (The game with the three dice.) Again, a pretty simple game, but I always had fun with it, and it was a nice way to try for some extra cash. Suikoden IV actually added a bit of a twist to it, offering two or three games to play with the dice, which was nice (though I always stuck with the game used in the previous titles).
Most of the mini-games that involved cards/tiles were always quite fun, so I'd love to see more of those show up again, as well. A new(-ish) game that I would like to see, though, is one that's been brought up already (by Pes, I think):
- Duels. One of the three forms of combat that the series is known for, and the recent improvements have been awesome. (Especially in V. Loved the full-motion attacks, as well as the countdown.) There never seem to be enough of these, though, so a mini-game featuring them would be awesome. Hey, let's take after the training dojo from Suikoden IV. Only, this time, have it based on duels. Especially if we're to ask for fully-animated scenes like we saw in Suikoden V, I won't ask for every character to be an option, but at least most of the melee-types. It'd also be amazing if you could not only choose from these characters as opponents, but as
playable characters. On that note, why not take after Suikoden V's chess/checkers with Egbert? Whoever you defeat in a duel will be unlocked as a playable character in the training duels.
- Dojo. Since I mentioned the training dojo from Suikoden IV, I'd like to see something like this again, as well. While it was somewhat of a cheap way to level up (especially with the level 99 trick), it was still a grand idea, if you ask me. Let's just have a dojo in our headquarters again, where we can choose to either duel or spar with full-party battles. Sounds nothing less than awesome, to me. Who's with me on this?
BattleParty Battles:- Six members. I won't settle for less than this "standard." With the exception of IV, the series has kept this, and I would like them to continue to do so. Aside from just being a unique trait of the series, with so many characters, having a nice-sized party like this is practically common sense. I just ask that the enemies are able to put up a good fight against such a party.
- Formation. While the formation has always been a part of these battles, Suikoden V introduced a whole new aspect of the party formations. I would absolutely
love to see these formations reappear in coming titles. The concept as a whole was just awesome, and I don't think I would change any of it. The only different idea I would think of is a free formation, where you could choose exactly where to put any characters. (Maybe throw this in as an unlockable later in the game.)
- Entourage. As far as an actually
useful entourage goes, Suikoden III technically introduced this idea, with its support characters. Suikoden IV kept the idea, and Suikoden V brought it a step or two further: Rather than just one support character, you had four extra slots to fill with your choice of support/bonus characters and/or extra characters that could be swapped in mid-battle, taking after a great idea seen in titles such as
Final Fantasy X. Again, would be overjoyed to see this return, and I pray that it does. (Again, I hope the difficulty of the battles will actually give us more of a reason to take advantage of this feature, though.)
- Another idea, similar to the entourage: A whole extra party that can be swapped. One again, this would only be good if the game's difficulty actually calls for something like this, but if the difficulty is high enough, then I think it'd be an awesome idea. (Personally, I'd prefer that if one party is wiped out, the others don't automatically replace them. That would make things too easy, despite it making more sense.)
Duels: See Suikoden V. I think they did it just about perfectly. Also, the training duels I mentioned as a mini-game would be terrific.
Full-scale War: Suikoden V, once again, really impressed me here. I had plenty of fun with Suikoden II's strategic battles, but Suikoden V's introduction of an active battle was great, I think, and the features provided were all pretty great. I'm not sure I would change much here, but if Konami can think of something better, then by all means, I would love to see what they have in store for us.
I suppose that's enough for this post. I've got some other things, such as character customization and such, but I'll save that stuff for a later post (seeing as this one's already pretty huge).