I haven't tested it, so I can only say that multiplayer will have unpredictable behavior at best and may crash the mission at worst.
I didn't add any multiplayer routines, so I know that none of the extra ballistic stuff is passed back and forth - stuff like ammo and whether you run out. Not to mention all the initialization when you start the mission and set your loadout in the first place. Best case scenario, the only difference will be that everyone flying will appear to have infinite ammo (just like with normal primaries). On the other hand, multiplayer might end up choking on something introduced with the conversion.
Just say that ballistic primaries are not supported in multiplayer in this release.