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FFA is really fun, but im kinda sad there is only 1 gamemode of it, im suggesting you should add stuff like FFA Custom Game, FFA and maybe even other generations. but thats juts a suggestion i would really love to see it though
For the record, it is already possible to challenge other users with any gen8 ffa format, thanks to the /challenge command. For example, if you challenge an user with the command:
You should be able to get something quite close to custom games (though this might not be the best command, i think it still has some ubers banned for some reason).
An example that might be easier to understand is applying, for example, stabmons rules to ffa challenges:
If you type /battlerules anywhere on PS, you will get more detailed explanations on how this command work, and how you can customize its rules. Hope this help!
The OG free-for-alls was mostly DuncanKneeDeep screwing around with his friends, and the Battle Royales had a point system to promote more agressive plays. Even DKD had to limit protect and recovery moves IIRC.
I think making FFA real competitive tiers and banlists would be an interesting problem. But for serous players, with the current limitations of using showdown, a serious battle would be difficult to make entertaining. If you can choose your own movesets then the best thing to do will just be to sit there and boost defences while everyone else KOs each other, matches would take ages.