FS should have some built in aspects that seed and encourage certain cultural things in it's community. A lot of the fighting game community has this culture of insularity, shit talking, dude-bro-ism, not to mention the "execution is the only thing that matters!", all things that run counter to Fantasy Strike's thesis.
There's a couple things, none which I would really consider "core" aspects, that I think can help with this. This are all more like fluff.
Make sure the announcer and characters are always super positive about winning, losing, training, everything. No taunts, no shit talking. Always stuff like, "You did great!" Maybe even some dynamic quotes where if you get a lot by a certain move from the winner, the character gives advice on how to get around that move.
A clever handicap system. Something more interesting than just reduced HP. Waterd pointed out playing as Dan is a much more interesting handicap. I remember Thelo talking way back in the day about limiting himself to a single button. The handicap should preserve mindgames but present an interesting challenge and unusual play style for the handicapped person that makes them learn and master different mechanics than their character normally focuses on.
A good built in tournament scheduler. For format, I'd love for FS to push Swiss instead of double elimination, maybe with a top 4 elimination? I know most big tournaments don't run a single screen, but I did run a weekly fighting game event at a bar for about a year and I think single screen "casual tournaments" would have worked pretty well if it were super easy to set them up.
A "casual scheduler". When running those events, people naturally starting using the "loser passes" system, which is fine, but I did notice that tended to create 1 or 2 to top players continually fighting a queue of "everyone else". It accidentally made it hard for the equally matched players within the queue to fight each other. It'd be neat if the game could automatically try to match up everyone with everyone, or at least keep matching up the pair that has gone the longest without fighting each other? I don't think you even need to worry about matchmaking in the skill level sense. In a small group like that, with quick rounds, just making sure everyone gets to play with everyone is great.