It would be nice to have a "room" setting in the Cabinet section. That would do it. If you use the reverb for a room feel, there is a slight modulation effect. I'm using that right now in fact.
That modulation drives me nuts and I've complained about it on Will Chen's headphones thread. I'm sure they'll address it soon, at least I hope they will.
You're idea to put rev'b in the cabinet section is good too.
I'm hoping they get on this as I'm sure there are as many , if not more, headphone users than there are amplified speaker users.
It really is the ultimate headphone practice amp.