You are going to have to adapt no matter what (if you are definately ruling out the 18-55)
I've not used the ef-m version of this lens, but the ef-s version was actually pretty good at 50mm, not a wide aperture, but the close focus mitigates and it can be used at f5.6 (you wouldn't want to shoot the nifty fifty at f1.8, focus becomes VERY critical)
Use the 18-55
Adapt a nifty fifty (personally I would buy the current, cheaper, in warranty plastic fantastic version or go the extra for the 1.4)
Adapt a shorty forty, great iq, keeps overall form down
Get a 22mm(35mm effective) keep your natural perspective as if you were shooting on a 50(80) and croppity crop.
You have 18mp, a 6mp crop would still give you an a4 photo quality print, the f2.0 will help keep your shutter up and your iso down (and the 22mm is great even wide open) the longer subject distance gives you a better chance with focus, and best of all, it's tiny, so keeping the csc advantage of small form.