I really like this idea, Scott, so yeah, a big thumbs up from me.
The challenge might be in the execution of the project? My original background is in economics, and one of the things that holds true is that most people will optimize their effort for financial reward.
Executed well, Micro-Credentials could become exactly what they are intended to be and result in a lot of fantastic professional development in teachers' areas of interest. If it's not done well, it will devolve to "what's the least I can do to qualify for the pay bump?" For example: Go to an ed camp, write a paragraph on how it changed my teaching, get more money. Find a summary of a book, write a paragraph about it, get more money.
I think the key part—that you mention—lies in the strong evidence of the application of the learning. If it's a rubber stamp process that can be done in just a few minutes then the system won't help much. If it's a solid process that requires effort and growth then I think it could lead to improvement in how kids learn.