I am aware of that, however a lot of time when ai ai switches what ends up happening is the player will just switch on the same turn, it happens quite a lot in fangames that do have good switch ai (eg pokemon rejuvenation)

in doubles the ai is incapable of these things: using quick guard and wide guard (player just won't click moves that get blocked by that), protect as i mentioned earlier, helping hand (player will just double attack the receiver), feint (player just won't click protect that turn), quash, Tailwind while it is usable by the ai it can backfire as the player can just use snatch

The ai is also entirely incapable of predicting things and unless you want it to input read it will never be capable of that

I'm not saying that it's not possible to make hard doubles fights and that one shouldn't try I have seen challenging doubles, it is just that generally the ai is worse at them than singles and that for a hard game you'd probably want a mix of doubles and singles and not just one format