I ran the mod through my automated tests (2.1.14 experimental)
What's interesting that in my test the building was actually 12% slower than RT2, but idle UPS has slightly improved, so I will have to look how that is done and possibly copy your approach
the issue might be that the queue is global instead of per planet, which can cause issues, and also manually placed entities while large blueprints are building sometimes get delayed pretty heavily
the grouped tile processing however is great, and I will implement something similar, as well as the retry delay and supply cache