Equipment/Proposed/Weapon addons
Optical scope (something like the svarowski scope) -adds accuracy (+20% of soldier's) -weapon uses more TUs in close range, but less at long range (dunno if it's doable)
Reflex scope (think R6 Vegas) -adds accuracy (+5% of soldier's) -weapon uses more TUs at long range, whilst using less in CQC
Supressor -weapon is weaker at long range -adds stealth elements
M203 (already listed)
Front grip -adds accuracy (+10% of soldier's)
Lightweight frame -adds TUs to unit using the addon
Thermal scope -adds accuracy (+10% of soldier's) -soldier detects aliens in his line of sight within 15 movement units
This is all I came up with for now, of course, graphic models are needed. Alas, we would need a new customization menu at the base (new option at the armory?)