That looks good.
Something like this?That looks good.
I would curve the topbar to somewhat follow the cantilever and attach a little lower on the headtube. Then make the rear a looptail with a nice curve in the chain stay that flows right up through the downtube to the headtube. The BB may have to attach above the bars. Then a slight backward curve to the seat tube topped off with a Brooks saddle and flat handlebars.
As long as I'm dreaming, a homemade springer fork with long springs would finish it off. It would have a vintage look to it.