Piaggio Grande, Derbi Variant and DS50, Atalla Master and LL4m, Motomarina Sebring , and Vespino are some of the larger framed mopeds I have had that were pretty comfortable. I am 6'2" and 200ish pounds.
I am sure there are a lot of mopeds that would be equally comfortable. I like having a long seat, helps me get in a comfy position. (I have had some smaller mopeds that wanted to wheelie when you scooted all the way back on a long seat)
Something variated or with extra gears is going to be nice to get you moving and climbing hills.