I would add a kind of bumper cars style mini game to the gold saucer, or maybe even go full on Mario Kart. Do I think the engine could handle that? Probably not, but the resulting madness could be extremely entertaining. Outside of just "doing stuff" in that mode, could be an MGP sink, a few people I talked to in the past are sitting at MGP cap, and you don't have to make it a huge MGP sink, want a special kind of weapon to use in the mode? Pay 1k MGP at the start of the match, and have a maybe a 5 weapon load out max. Each weapon gets 1 charge.

And for inspiration, I'd go for the original SNES mario cart, some weapons are better than others, but if each weapon can only be purchased 1 time and you get a max of maybe 3 to 5 weapons, well there you go. For modes, you could have a race mode, and the objective could be "winning" the race, but you know you'd just focus on pushing your friends off into space . I would. Then have the classic death match style as well. This game would have to be a bit better programmed than the chocobo races tho, imo chocobo races are too stiff and jerky and "robotic" feeling to feel well, and the controls are horrible in my opinion, and that might be a server or engine limitation. Ok that's what I'd add.