When Voldemort's fragile soul fled to Albania, either pre- or post his adventures on Quirrel's head, why didn't Snape travel there and seek to draw him out of his hiding?
This, to me, seems to be the best way to use Snape as a double-agent. This plan becomes much more feasible given that
- Dumbledore suspected that Voldemort was indeed hiding in Albanian forests,
- and Voldemort himself said that if his followers actively looked for him, they would succeed.
That indicates that if Snape attempted to find Voldemort, using the information he had access to as both a Death Eater and member of the Order, then he would probably have succeeded.
At that point, it would have been a matter of triviality to deal with Voldemort's soul. Perhaps he could not be killed, but he certainly could be contained.