I agree, but i would be curious to try it. An honestly i dont think your keeping the integrity of the bike by putting a gsxr. front end on the bike, and hacking the rear fender and frame. Im thinking of the possibilty, these vintage honda engines are amazing
It's not about keeping the "integrity" of the bike, but as I said "some of the character." With all due respect, if this was about keeping the "integrity" of the bike, we would not be discussing a cafe or restomod. We'd be talking about a restoration or survivor style bike.
The 550 engine in stock form is not terribly potent, but the bike is light enough to make it fun. If you haven't seen it already, check out the Thorn built by Ian Halcott and Twinline. A punched out Kawasaki 550 twin motor mounted into a braced 550 frame. A light, nimble little track bike. Braced like hell, because these CB frames flex A LOT.
I'm sure you could put a 550 motor into another frame, but at that point, why? There are much more capable power plants available.
Just my $0.02. If you don't like my opinion, that's perfectly fine.