When it comes to the transition process from the old C/AL based solution to extensions, Stefano Demiliani in the latest
Simplanova blog post suggests you to start thinking about the question of what you want to achieve. The first challenge he sees the partners are facing when they start moving a C/AL solution to an extension is how to define the architecture of the new solution.
What are the available architectures when building the new solution (from the C/AL to Extensions)?
Stefano reviews the following three architectural options:
1. Monolithic extension (multi functions)
2. N separated extensions
3. Base layer (hidden extension) plus N extensions dependent from the base layer
More details about those solutions you can find
here.