Its generally accepted that BMWs aren't as immaculate as most V-twin cruisers as we actually ride our bikes to the rally rather than trailering them..

But anyhow, if you get your wheels powdercoated then any automotive type cleaner that is safe for paint should be good on them. On unpainted alloy surfaces like the engine case, valve covers, cylinder fins, most just use a general purpose degreaser and some elbow grease with those nonmetallic scouring pads like you use for no-stick pans. Don't use steel wool as it actually does scratch the alloy surface and it leaves tiny bits of steel that then begin to rust.
Some of the really obsessed may supplement the non metallic scouring pad things with a drill or dremel tool for polishing. The key thing is, these are BMW engines - they aren't meant to be shiny like chrome harley engines

I think that your bike looks quite nice and tidy as it is - you just need to get some battery sidecovers for her and paint them black..