I think having 2 chains, one with segwit and one with a block-size increase is the optimal solution.

There can be only one Bitcoin; compared with alts, the advantages of Bitcoin is the network effect, the brand name and (arguably) the security offered by the crazy amounts of CPU-power owned by the miners. Split the chain, and Bitcoin is dead.

In the late 90s there was one standard for online chat on the internet, it was IRC; everyone was at IRC. What happened? The network got fragmented due to arguments on how to fix the problems on the protocol level, and instead of IRC we got a lot of commercial, centralized, closed chat-platforms, and some few open chat platforms used by nobody.

Roll forward some years, and we'll still be stuck with fiat (a jungle of different commercial centralized actors) and some few dozens of crypto-currencies used by nobody.