As a complete non-expert: On the one hand, looks like decent cleanup. (IIRC, engines in particular will not be missed). On the other hand, breaking compatibil

As a complete non-expert: On the one hand, looks like decent cleanup. (IIRC, engines in particular will not be missed). On the other hand, breaking compatibility is always a tradeoff, and I still remember 3.x being... not universally loved.