This is a "bet the company" change you're asking to help sell. For all concerned, it might be better to recommend an alternate approach where the new technology is explored in the small scale first.

If there is any way they can expend some resources on this new path, instead of risking the entire existing revenue stream, you'll probably get buy in for that.

I really don't think you want to "die on this hill" - https://en.wiktionary.org/wiki/hill_to_die_on

However, since it isn't your call, I can see how you might have to do it anyway.