I think even the lightest two handed rod is still a little tedious and tiresome for long bouts of single handed casting. That having been said, I've never spent time with anything lighter than a 7wt switch rod.

Personally I'd look for a fairly long single handed rod (10-10'6"?) with a weight forward line, even some of the switch lines like Rio's Switch Chucker cast well one handed. They don't strip or mend well though and so perhaps more traditional heads and tapers are better for this application. For multipurpose use I often over line my 10' 8wt with a 9wt switch line and am happy with this setup for swinging and single hand casting.