Bit of an update on this an v1.0.
I was busy all weekend with some friends from work, but got in a bit of time on the controller on...Monday? Tuesday? something... I think I got it working, but the motor I was testing it on is a bit..slow to respond? Also, I misread the spec and got the wrong value pot for the throttle. I need to work out getting the hall-effect throttle on the scooter working with it anyway though, so I'm thinking I'll just get that working for testing rather than bother finding a 1M pot.
On the v1.0 front, I got a line on a GS1100GL. Going to take a look at it on Saturday, and likely picking it up then. Full title, so no worries there, and it'll have way more space for the components (mainly for the batteries) than the 450 at not much more weight. Plus, it apparently actually even works now! Needs some carb work, but I'm thinking I might get it road-worthy and ride it for a bit before stripping the ICE off and converting it.
It is a shaft drive, which is interesting but apparently quite a lot less efficient than a chain drive, so I'll probably be pulling that and replacing it with a chain drive.
...and then I'll have a full, functioning, GS1100 drivetrain lying around...I'm sure I can find something interesting to do with it.