Nostalgia is a very strange thing. I suggest that in their era Nortons were better than most other motorcycles. Wishing that was true now, will not make it happen, The 961 is a development which uses experience from modern motorcycles. But the 270 degree crank and balance shafts in the motor, have not yet been proven to be excellent, by road racing. If the bike never gets raced, we will never know how good they are, unless we buy one. And then our assessment would be subjective anyway.
An XS650 Yamaha has a crank with a centre bearing, but the cylinder head design is not quite right. The Paton 500 is probably the untimate in vertical twins.
A rotary engined road bike might use too much petrol. And if you need to give it a rebore - might be a problem ?