Well, I think that teleport would work if he casted it (it only effects the caster, and it works though python, and I don't think it can be resisted), but it is now a Chanter-only spell; there is no way for him to use this. He is immune to spells like haste and heal though.
If you meant using an Obsidian gate, this is quite possible (it is not a spell at all, but the airlift ability from vanilla), but he would have to be in a city with the gate. I believe that when you capture him he will be moves to the attacker's old tile, out of the city, so you would have to move him into the city first.
You can still load him into a Ship (requiring he be in a city so the ship can get to his tile) or into the Trojan Horse to move him.
Acheron (like all other Beast Class units) can get the mobility 1 (but not mobility 2) promotion when he gains a level. It is often best to weaken him with a wave of weaker units to give him some xp, and to capture him before the Barbs can purchase a combat promotion instead of mobility.
(In my modmod you could also load him into a Tesseract, my Dimensional 3 summon, and then paradrop the summon and its cargo him to any tile within a fairly large range.)
