Thanks for the input.
I understand that one design diagram doesn't answer all questions.

It's purpose is to have a guideline while developing the engine along the way. It's a combination of my last engine and things I ran into.

And to be honest, I will for sure run into things and will improve it along the way. What it saved me already is lots of time writing duplicate code or unlogical inherited classes etc. Especially the part with the 2 buffers, reducing all scene classes by almost 50%.

So again, Thanks.
I'll surprise you with a nice demo in a while and perhaps a new game using the engine.