Quirrell's Parseltongue statements could use a close reading.

I cannot be truly killed by any power known to me.

This could just mean that the Pioneer horcrux prevents him from being "truly killed".

And your girl-child friend sshall be revived by me, to true life and health

This seems quite explicit. Quirrell thinks that he can bring Hermione back to life.

Harry: You already have an idea for what you want from me. What is it?

Quirrell: Your help in obtaining the Philosopher's Stone.

(Not in Parseltongue.) Quirrell later asks Harry in Parseltongue to promise to help get the Stone, but he never says in Parseltongue that help getting the Stone is what he actually wants from Harry.

I do not intend to raisse my hand or magic againsst you in future, sso long ass you do not raisse your hand or magic againsst me.

Does this rule out Quirrell transferring his soul into Harry's body (wiping out Harry's identity and reuniting with the Tom Riddle groundwork that he laid in Harry's mind)? Because without this line, that would be my leading hypothesis for what Quirrell actually wants Harry for.