Personally I think a slight XP gain in automission would not be a big problem.
Something like 1/10 of the normal XP gain when you play it, or something similar.
I don't mind either way though.
What I think automission is useful at is to skip missions when you don't feel
like you want to do them right now, because you research something, or
want to wait for another mission etc... it just allows you to skip time a bit
and this is a good feature in itself, with or without XP
After about fifty times through the same old downed fighter/scout it's just not all that awesome anymore. If it was me I'd auto mission through all the regular map tiles that I've seen already, and then stick to when I need live aliens, or it's something super cool like a special mission.
With a terror mission and three downed fighters/scouts on the geoscape it just becomes a not-fun chore. Or maybe I should start situating my bases with half the radar over water.
I also agree, perhaps we can come up with more ideas to make more and different missions.
I mean, ideas to lessen the frustration... perhaps more non-standard mission types?
Something crazy, like "rescue scientists" ... and if you succeed here, you get a few extra research guys for frees.
(It should have to be easy to implement though... we don't want to distract too much from the main game with these small ideas.)