So this is something that's been discussed a couple times, but its been a while since it came up. The biggest issue that comes up in discussions is that it makes the ruleset more complex whereas a significant portion of the playerbase favour simplicity. This is especially an issue for newer players, who wouldn't expect that kind of restriction on their gameplay. The other thing that doesn't get talked about, is that it would need to be coded into PS, whereas bans are much easier to implement.Is there a reason a simple Fly/Dig Clause hasn't been tried? I get why the invulnerability after being fullpara'd during the move would be a problem, but with a simple rule like:
"You must complete the move immediately if you were fully paralyzed during it, you may not switch pokemon or select a move besides fly while using fly"
then the invulnerability glitch would be a non-issue.
Sleep Clause exists so that sleep moves don't need to be banned. So there's already a rule governing player behavior, preventing moves from being abused without needing to outright ban them.
The above rule for Fly would even be cartridge-friendly.
The only circumstance where I can see this being a problem is if someone runs out of PP during the move, at which point a cartridge implementable solution would be to say they've rendered the game unable to continue, and have thus forfeited the match. Which if you have only one or two PP left and you choose to take that risk, then that's a calculated risk that's ultimately on the player if it doesn't work out for them.
I know the whole Fly/Dig thing is something people get tired of responding to, but usually the answer is either because fixing the glitch to act like later generations wouldn't be cartridge accurate, but letting the move go unregulated would just be absurd. I don't get why a rule like the above shouldn't be implemented though.
None of the points I just mentioned would be dealbreakers if the moves were integral parts of gameplay the way sleep is, but Dig/Fly simply aren't, so it ends up not being worth it. Admittedly, in lower tiers there's a theoretical argument that they provide coverage, but I don't think it's terribly strong, and there isn't really any practical evidence that these moves would be viable (to my knowledge they've literally never been considered viable in any meta where they're allowed).