Does are just for looks. Far as I know, they fire the same way puffy ack from a CV does. If we do get the 88mm, it will probably be only as an anti tank gun. 88mms had no proximity fuses, which would make it a whole lot harder than our point and click 5" guns.
I suppose it would replace the puffy ack guns in the EWA and MWA as an AAA gun. But that would probably take a whole lot of work to redo every map and replace all puffy ack guns with an 88mm.
In the LWA however, it would be pointless to use. The 17lber already has enough firepower to kill all tanks, there's no need for the 88mm despite it's importance in WW2. (IIRC, the 88 had more penetration than the 17lber, so then why would anyone use the 17lber if the 88mm is available?