For the autocannon you have two choices:
1)
WYSIWYG. Do you or your opponent
see LBAC? No? Then just don't fire it.
2) Treat it like a
SMs bolt pistol. Doesn't matter if it's modeled or not, the model still has it. FIRE!
* If I couldn't model the
AC decently
I'd default to #1.
Of course the best solution (aside from buying the correct model to start with

) is to talk it over with your opponent(s)....
For the missiles?
Only model 4 missiles on your lightning.