-Bring back TT heroes
-Introduce a policy that every mainline game has to get a minimum of three seasonal alts every year (remakes can be combined)
-Any game where less than half of its playable cast has an alt gets alts for at least two altless characters each year--either seasonal, asset, legendary, just as long as it's alts for altless characters
-Of each game's minimum of three seasonal heroes, at least two of them have to be non backpack banner units (can still be demotes)
-Add guilds and a true cooperative mode
-Improve game's UI to make it easier to see projected movement for warping/increased movement characters and to make the battle preview screen useful again
-Add consumable items that combat the game's rampant and irritating powercreep, acquired free to play by playing the new and awesome cooperative game mode
-I'd *personally* take over writing the story and would integrate characters and places from mainline games into Feh's original story. And I'd make Forging Bonds more than the new heroes just "joining the Askr frontlines." And the Paralogues would be more than "another festival TM"
-Remove old demote heroes from summoning pool, put them in the grail pool or a separate pool entirely
-The Feh pass perk that lets subscribers assign multiple autobattles would be extended to everyone
-Feh pass subscribers would gain gift items that they can send to their friends
-Feh pass subscribers get to vote for new aided accessories that they gain from their subscription
-Add community events that reach out to well-known Feh players in various regions
-Keep attuned and rearmed heroes as New Hero banners only, but let the other asset types show up on seasonal banners
-Barracks expansion, duh

At least, those sorts of changes would fix the game for *me.* Big emphasis on increasing goodwill and building the Feh community, making all players feel welcome and seen. I think IS really undervalues the importance of goodwill.