Let's suppose there was a change X to the Constitution that a plurality of English Canadians disliked intensely, but would prefer to secession. And let's suppose that the median resident of Quebec would oppose secession if X became part of the Constitution, but not otherwise. Will X get enacted?
No. Secession will happen or the status quo, but not X.
But why? Wouldn't it be the most efficient result? What about Ronald Coase?
There are many reasons, all of them I suppose subsumable under the term "transaction costs". Too many veto points is one answer. But another is that the implicit deal "Enact X and we won't separate" is unenforceable. The ROC could agree to X, and Quebec could still have another referndum in a few years.
ROCkers may be unfashionable, but they are not stupid. So, X is not going to happen.
The only possible way out of this is if Quebec would agree, in exchange for X, to an explicit supermajority requirement for an independence referendum in the constitution. If the Constitution said, "A province may leave Canada, if, and only if, 2/3 of the electors in a province-wide referendum vote 'Yes' to the question, "Should [your province] leave Canada and become an independent state?", then I bet you could get ROCkers to agree to a lot in exchange.
The thing is that there is no X such that Quebec would give up the ability to leave on a 50% plus one vote in exchange. It doesn't exist. So it is secession or the status quo.