The flywheel seal on my motor is marked 12 22 14 TG (I think). I haven't pulled it but it looks like it would fit a 21 ? X 12 X 6 or 8 mm sealed bearing in place of the oil seal. Is there something wrong with the idea of fitting a sealed bearing in place of this oil seal too Scott ?

Issue will be if case O.D. is of a normal bearing OD diameter, Width equal to a known bearing of that diameter, ID with above dimensions allowing fitment.
* Lastly if crankshaft has a straight diameter from OEM bearing out to where a second bearing would reside ? ( Zenoah cranks drop @ .0015" in diameter on mag side )

Yep. You're correct. I've measured more carefully & it's 22mm. There's no bearing available in that size. - pity.

NEITHER crank works in the compact case g230pu/g231pu/g260pu series engines.
There cranks are TOO short on the magneto side so fitment of the small finless flywheels used in the PU won't fit