Writing a custom render engine for blender

I’m planning to design a standalone OpenGL software for non-photorealistic rendering. (using C++ and Python)

I also plan to design it in a way that it can be used as a render engine for blender.

Since I’m inexperienced in writing a render engine for blender, I was hoping to hear from anyone that has insights on key challenges, downfalls of implementing one instead of alternatives (e.g. writing a model exporter), etc.

For example, if I write a render engine now, will it require constant maintenance in future Blender versions?

How realistic is it for a one person working on it in his spare time outside his full-time job to create a render engine for blender? Is the scope feasible?

What are some design considerations in terms of best practices, etc?