Mezzio to gradually move away from MVC

What is the strategy to gradually move away from laminas-mvc to something more modern using Mezzio?

My company wants a modern system using api backend and a react frontend.

I’m thinking that:

  1. the old MVC project could be put into a legacy folder
  2. Mezzio serves the modern app (react frontend api backend)
  3. If a route hasn’t been made in the modern app, Mezzio middleware could serve the legacy route instead of page not found.
  4. The backend database factories written in doctrine could be shared between the modern and legacy code.

This would allow the legacy app to be actively maintained in the legacy folder, but also allow the legacy app to be gradually re written in somethibg more modern in another folder without a significant headache.

I feel like I’m shooting in the dark.
There are no resources online I have found that suggest moving a big application this way.

Any suggestions?