I'm starting to work on creating my own Fire Emblem game as of recently, and I thought it would be a great idea to ask you all what kind of character you would like to see.
For those who don't know already, Fire Emblem is a fantasy setting. I should definetly be able to add humans and dragons (manaketes) to the game, though anything beyond that isn't guarenteed.
If you have any ideas, please put them in the comments. A submission (sounds way too formal but idk what other word to use) should have a name, species (human or dragon/manakete), a gender (or specify agender), race, and a class. If you want to, get creative with the classes, as long as I understand what you mean, I should be able to get them to work within established FE classes. If you want to get really creative, come up with a physical description, and/or even a personality!
I'll turn on upvotes temporarily once post traction slows down, and whichever character has the most upvotes will be added. This means that, even if you don't want to design a character, you can support your fellow hexbears who created characters that you like. If there's a lot of submissions, I can pick the top few and do a recount, and then add the winner of the recount. If I have the space in the ROM, I could possibly even add multiple characters.
If you end up submitting, thank you, and I look forward to seeing what you all come up with. 
I forgot to add, if you are interested in any established details about the game/story, feel free to ask. I would honestly love to talk about it!
More gameplay mechanics than character design:
Giant characters that are actual giant characters as in they take up more than one square on the map. So you can have a giant character that takes up a 2x2 square and who can travel twice as far as normal 1x1 square characters per turn. To balance this out, they have 0% dodge (and can't critically dodge) and can't fit in narrow 1 square pathways. They also take cumulative damage for each square hit by an aoe spell, so if an aoe covers the entire 2x2 square, they take 4x the damage as a normal character would.
Characters that affect terrain. So like a sapper character that tunnels through impassible mountains, engineer character that builds a bridge/raft on bodies of water, a pyromancer that turns a forest tile to a plains tile (lore explanation is them casting a fire spell to burn the forest), geomancer that spawns a mountain to box enemy troops in.
I don't know how feasible this would be for what you're trying to do. If you're talking about creating a ROM hack for a GBA FE, I don't think you could do this. Maybe you could have an aquatic/amphibious class that has massive movement bonuses on water but take massive movement penalties on land. I think the pirate(?) class in one of the GBA FE can walk on water, so maybe you could do something there where you give the character a natural high movement value but give them massive movement penalties on any terrain that's not water. I think having a mermaid character or even a fish character is pretty out there for a FE game since those games mostly take place on land. But you don't necessarily have to have every battle take place in an open plain, a castle, or a cave. You could totally have sea battles in an SRPG.
Pirates are definetly something I could do. There's an archipelago, so I was already planning on at least 1 level with a lot of water.
Believe it or not, I have seen someone make use of Dragon Veins in a GBA ROM, though I have no clue how they got it to work. If I could get it to work, it would be cool to have certain mages eliminate certain terrain, or have physical classes break through pillars and such. If I could work this in, anything could be possible, and I could add dragon vein in like a class effect. I would just have to try to make it so changing certain aspects of the map wouldn't break the ROM.
I thought of some more characters:
A character that has high movement, high constitution(?), and high defense but low attack and low speed whose basic function is to rescue people and ferry them across the map. Lorewise it could be some golem that's programed by its creator to avoid violence. Maybe they can also get the exp bonus skill so leveling up the character won't be a complete slog.
Survivors of a naval expedition from a faraway land. The survivors could be scattered across the game. It's also a good way to introduce characters that aren't just Europeans/white passing like the vast majority of FE characters. Real-life example is something like Mansa Musa's predecessor sailing across the Atlantic never to return.
A pair of characters, one who is a legendary person and one who is a complete fraud pretending to be the legendary character after the legendary character goes missing. The fraud could be heroic in their own right with people confusing the heroic acts of the fraud with the heroic acts of the legend.
I really like these! The idea of a foreign expedition being scattered and lost sounds like a good one.
Yeah I'm not planning on letting this game suffer at the hands of the Cracker Curse.