Nicotine on Maemo 5 would be nice, yes. I had a look at how they build the UI (converting .glade files to Python source in that case), and stopped there. Reparenting widgets into a bare Maemo 5 UI and simply hiding Nicotine's windows is probably the easiest way to do it, even if it's not very good performance-wise, as lots of unnecessary stuff gets created and probably updated in the background.

What you shouldn't cripple: Saved searches ("wishlist").

Make first-time configuration automatic: Hardcode the downloads path (/home/user/MyDocs/Nicotine maybe?) and generate a random username and password on first start, so users don't have to fiddle with the settings dialog. The downloads and uploads list can probably be in a separate StackableWindow (accessible as AppMenu buttons?), and the searches probably a list of searches that - when touched - will open the current results of the touched search in a new StackableWindow. The only usable search results filter is probably the "free slots" filter.

Keep it plain and simple