@Stockton Senor in order to modify A Better Advent's version of a sectoid you would need to modify the psi reanimation of the sectoid from the other mod to change it's targeting from dead corpses to hostile units. Take a look at the code in this mod and look at A Better Advent and look specifically for the sectoid class. and find a true or false statement for the targeting of Psi reanimation and if it says exclude dead units=false, change it to true. And change living units to true and exclude friendly targets.

Interesting mod, but a slight question: How would I go about modifying it to effect Sectoids from other mods such as A Better Advent?

Lordabizi it functions as shown and trust me this buffs the Sectoids a fair bit up in terms of being dangerous to you and your soldiers. Here is a scenario I experienced when using this: I was pinned down by several pods and one of my soldiers was effected by it and they were then converted and since they were a decent soldier and I was pinned down it I took a bit of a loss, but quickly flashed the Sectoid and won the mission.
Also when I recovered the soldier I noticed he took some damage from being converted and that was because the health for the zombie is determined by the stats of the Sectoid and his health was reduced so he took some damage but recovered quickly. So all in all I'd say the Hypnosis ability is a much needed buff.

it would mostly likely give you your soldier back if they can't be picked up.

You should be able to pick up the soldier if they are then turned into a corpse. if it doesn't work it would either capture your soldier or give them back to you.

It is an interesting idea, but how does it work in non-sweep missions? For example in VIP council missions. Can you pick up the body of a soldier that was hypnotized?