Progress and improvement is fine, great even, but consistency is more important. If you change a pattern, change it everywhere.
Document the old pattern, document the new pattern, discuss, and come up with a piece by piece plan that is easy to ship and easy to revert if you do screw things up.
Unless the old pattern is insecure or burns your servers, that is.
I think the point is, either actually commit to doing that, or don’t introduce the new pattern.
The down side to this that I've experienced more than once, though, is incomplete conversions: we thought we had agreement that the change should be done, it turns out to be more difficult than planned, it gets partially completed and then management has a new fire for us to fight, resources are taken away, so you still have two or more ways of doing things.