Thor wouldn't be able to distractedly banter with Loki, they'd get in their usual brotherly blood feud and then there'd be noogies, purple nurples, and usual brotherly fighting. Tony Stark's power comes from his ability to banter with Loki on somewhat the same level as him which is saying a lot when it's a discussion between a demigod and a mortal man.
I wonder if explanation is given on why Asgard isn't stepping in to stop Loki's plans like they did to stop the Frost Giants' go at Earth? Seems to me they'd see themselves as being just as "responsible" for Loki as they would the Frost Giants. (I'm guessing whoever Loki gets "fully back", how Thor gets back precludes any involvement from Asgard.)