you are making a lot of assumptions. First of all there is an agreement and any big miner that wants to breach the NY agreement will not be trustworthy to its clients and the ecosystem and will cause its downfall. Second, mining something that does not have the best developers is a risky proposition unless you think all bitcoin software is ready to go. Bcash has as a developer who? Third, you need to convince all users and shops to change software to support bcash payments. And that all sounds very logical to you.