my main qualms about this aren't really the same as others. i do agree that it's very luck-based, but i really like using flinch parahax, which i feel is a legitimate strategy as well, so i have no problem in-and-of-itself.
i feel like there are two problems with prankster + swagplay that differentiate it from other forms of strategies that rely on luck though.
first, it's very difficult to plan ahead to counter the strategy due to prankster giving priority, and swagplay can be its own worst enemy with hax going the wrong way. what i mean by this is, it's almost pointless to build your team to counter the strategy, because swagplay can potentially cause more damage to itself than any counter strategy. you just play normally against swagplay and hope for the best. this is only really a problem, as others have mentioned in the species clause discussion, in that any amount of teambuilding done to counter swagplay pretty much goes out the windows when you play an entire swagplay team. which brings me to point two:
i see a few people making teams entirely of prankster swagplay users seemingly for the sole purpose of annoying other players until they forfeit. this, to me, is similar to the endless battle problem. it's not so much to me that it's uncompetitive (mindless teambuilding relying on luck and bad player beating a better player, etc.) but rather unsportsmanlike (making it an unenjoyable match for your opponent in the hopes that he or she leaves). i suppose we would need some statistics to show us how effective this strategy is. how often do they win by forfeit. how high of a rating do they really get, etc.
i know the two aren't entirely the same. as i said, i feel that swagplay a legitimate strategy (and don't feel that way about endless battle), but in a 'this is why we can't have things kind of way', i would agree to a swagger ban. i would rather have a new rule that simply restricts swagger to one, two, or so per team, but i feel that all of the other parts of prankster swagplay are still viable without swagger that i could support just the simple ban.
tl;dr ban swagger (but i would prefer a simple move restriction if anything)
one final caveat as well, i feel that this might 'run its course'