This sort of logic has been discussed in various different Policy Review threads (see
recent example), not as a warning for players, but to more closely align to how Sleep Clause would be enforced on modern generation cart games (that is, you can't click a sleep move if you've already put one opponent's Pokemon to sleep). That sort of logic would need to be implemented server-side though, not client-side.
Clause explanations at the top of the battle naturally get overlooked, because you're focused on the opponent's team or the Pokemon immediately in front of you on your screen, not the text in the top-right. Linking to outside stuff mid-battle is also ripe for problems, where a player clicks an article, forgets they were in a battle, and gets timed out because they were reading that (remember we're keeping new players in mind here).
I think the simplest solution is just to re-print what the Sleep Clause Mod does when it gets triggered (if it even needs a "solution"). I am heavily opposed to handholding people in suggesting what moves they
should click
. Even granted that Sleep Clause Mod isn't a cartridge interaction, we don't handhold interactions on anything else. We don't say "hey, don't click Fake Out after turn 1!", or "hey, don't click a sleep move here in Electric Terrain on this grounded target!" or "hey, don't use Poltergeist here, they don't have an item!" or any other number of moves that can fail. Understanding how the format works is a part of playing Pokemon.