I think the big shift in my perception was that it looked to be Castiel who made the approach, so (and I'll have to rewatch) the "he prayed for this" was a bit of a stretch.

(I kinda want to see a "Dude, 'use us for Thy will is just standard boilerplate when I say grace, I didn't mean to POSSESS me!'")

In my personal canon, the vessel was completely relentless in demanding to be of service, to the point where it had already ruined his family.

I totally need to finish getting ready to travel, but I'm wondering if I can squeeze in another watch -- ha!