When I wrap a leather handle on a bow I always glue with barge cement right over the poly or tru-oil finish just as you described.
I've done at least 50 bows like this and never had a problem. I've gone back and replaced a few of those leather wraps for a better
looking leather or for a different look and all came off easily even though they were tight before I removed them. Padding out the
belly or back with leather as you described to fit your hand also works well. Its like anything else, a little practice and trial and error
and you'll have a nice wrap.
Show us your results, good luck Matt.