I believe it will be standard ammo and lethality.
Personally I'm not looking forward to the Ju-88 round. If I had to reconsider I would definately consider putting the Ju-88 on the 'Shouldn't use this' list.
After all there are Bomber/Attack planes with no pilot operated guns and of course they can't be used. They include the B5N2 and Ki-67. While the Ju 88A-4 has a gun, it certainly has very limited ammo and it isn't very lethal.
Of course some Bomber/Attack planes do have pilot operated guns and some of these are regularly chosen. They include the A-20G, Boston III, D3A1, IL-2 Type 3, Ju 87D-3 and the SBD-5.
Looking at the Ju 88A-4 it actually looks like the gun the primary trigger fires is infront of the co-pilot. That fact should eliminate it from the available planes, IMO.
In fact I am going to discuss this with WMLute and come to a decision before we hold SatKOTH.