Mayuri and Urahara would probably be able to take down any enemy other than lille. Probably noone other than them would stand a chance VS Askin, and Pernida's powers would be too confusing for anyone else to figure them out.
Lille was just to absurdly unfair to be beaten by any non "SurprisingMagicLilleSlayingPaddleDeusExMachinaTM"
and of course, Aizen would beat all 4 of them at once with laughable difficulty. merely them being able to survive being exploded is no excuse for him to lose.
Also, Nemu could beat Gerard, because she is confirmed to be stronger than Kenpachi. (Pernida mimicked Kenpachi's strength and speed, Nemu still speedblitzed it) All she needs to do is throw Gerard off the Wharwhalt.
That said, if it was Mayuri vs Gerard, then it wouldn't come down to Nemu vs Giant Gerard, and i'm guessing the fight would be ended sooner with some kind of magical drug.