I think it can. Everything should be in the .atom files.
Open data.kfs with winzip and find:
army_droideka.atom
that should be the repair droid. Then find:
army_beholder2.atom
Open both. There is a line:
attack=droideka_attack_uni.bsa/fr:25:50/r:0:20
while corresponds to this one:
attack=beholder_attack.bsa/fr:25:50/r:0:22
In theory, replacing one with the other should give the droid ray-like attack. However, back up the data.kfs file in advance. In addition to that, I think there may be a problem with the animation, since the ray attack from the Beholder comes from a higher altitude point (due to the fact that the Beholder is taller than the droid).
I, for one, would love to see droids fire lazers as well
I'll try to make the alteration as well and see what happens.
EDIT: Hmmm, theory went wrong
I'll check something else. In the army of the light mod there was such ray implemented on a mage.