Every flight sim I can remember had this feature: you fire missiles or drop bombs, your plane got lighter. Give each ammo type a mass per round rating and reduce the add-on's mass as you deplete the weapon.

Oh, and reloading should take a little time. maybe 5 seconds?

This one is a keeper though, and a nice touch.

Yes, this is something that has been frequently suggested over the past few years. I do like it.

The weight is a great idea the reloading take time is a terrible one

+1 for the weight.

+1 on weight

+1