I recently tweeted about how adding seemingly minor features can unexpectedly snowball in to a significant amount of work. I thought it was worth writing up in...
I don't understand why exactly C3 ever attempted being backwards compatible with C2, feels wrong to me since this was supposed to be a new engine, a new start, but either way I appreciate your efforts and I feel my money is well spent here. Do what you gotta do.
Even now, hundreds of C2 projects are imported to C3 every day. It's a major feature for a lot of people and makes it far easier to upgrade to C3, resulting in more C3 sales.