I suppose the same case can be made for the Medikit. Sometimes I used it to heal downed aliens so they don't bleed out before the battle is over and can be captured alive.
I suppose for Darts, a mod could be made where the aliens are vulnerable to a certain damage type (e.g. E115?) while immune to others (regular stun). Then capture weapons for each life form group can be made. I believe, however, stunning in itself is hard-coded, but with scripts anything is possible.