I can see the analogy you're making, but it's not entirely accurate. Segwit didn't fork a separate protocol into the consensus. I have doubts that Core would merge something like that, especially given the security trade-offs of a drivechain. Segwit was much less contentious than that.

I'm not particularly comfortable with the precedent of miners forking in sidechains, on which users blindly trust those miners. I think economically important drivechains may skew Bitcoin's mining incentives. I'm not sure. I'd like to see more convincing game theory suggesting drivechains are a good idea before considering enforcing them at the consensus level, that much is certain.