Investigation and understanding some others code is a hard work. Especially if design stage was skipped for this code. And this work is far less fan than creating something from scratch.
Some of PGDCE developers has own projects, including almost complete engines and similar concept-wise to PGDCE.
And some parts of these projects could be partially reused during development of PGDCE. There is one restriction - the code should comply with PGDCE architecture and coding standards. So probably it should be slightly rewritten.
Reusing the whole engine is not suitable in our case.
As of engine focus: I think there should be no focus in a basic framework.
Current games often combine multiple genres and multiple kinds of gameplay.
Still, for certain project a dedicated extension can be used which is not suitable to include in basic framework.

BTW, are you still with us?