I'd agree engineswaps are just a waste of time/money. You already mentioned you're used to bigger bikes, which leads me to assume you're also used to having powerful multi piston, multi caliper brakes and shockabsorbers that actually... well... absorbe shocks. So I also assume you noticed the quannon doesnt need that because of its limited topspeed and weight.
Now lets say you'd manage to squeeze a 250 - 500cc block inthere. You'd be increasing your bikes weight significantly (its not just the weight of the motor, but think smaller parts like sturdier mounts, all kinds of brackets, bigger radiator etc. etc. aswel). So you now have to find a front fork with decent shocks, rotors, calipers, a fitting rear shock (they exist but arent exactly cheap), exhaust etc. and you need to find a way to assemble it all ( rest assured nothing will fit without lots of modifications ).
And even if you do manage to make a well engineered bike out of it you'll end up with a bike your wife doesn't want to drive anymore cause the characteristics she loves of the quannon are now gone (lightweight idiotproof with in-law power) so you end up driving a bodged inbred bastard that still doesn't meet up with bigger bikes you may have owned earlier.
If I were you I wouldnt bother. Give the bike to the mrs. and start saving up for a bigger bike for yourself.
