If I had access to a store of different parts, I would certainly try them to resolve my problems. As has been said, most people (like myself), haven't, so we have to make do with what we have. For me, the challenge is to recognise a problem and try to fix it in the least expensive and best way possible. This is because I could easily buy a part which is incorrect, then have the problem of taking that risk again, which gets pricey and complicated.
A lot has been spent on this bike already, so I really want to make use of what I have. The gearbox cover I've just bought was cheap, but my reckoning is that I can either refurb this one and put it on, or put it on and refurb the existing one. I could then sell one of them for roughly what I bought it for but with a good clean up, etc?
There's also the challenge and 'fun' of fixing a problem - which I like. Skimming a bit off the cush sleeve should solve my alignment issue. As for the clutch adapter, I've got that nice and tight on the taper with an adapted key - if it works as well as it should, I'll be happy. Like someone said recently, I could replace the chainwheel, adapter, possibly plates, possibly mainshaft, and buy the appropriate cush sleeve, but I can't keep throwing money at it that I don't have. Keeping it on the road is my main priority, even if I have to depart from 'standard'.