There seem to be two independent problems.
First, make an updated version of the IIAB OSM. The goal is to
understand what are the computer requirements to do this and how long it
takes and then be able to make a new version whenever needed.
Second, make available more detail than IIAB OSM
The idea of pre-rendering some of the tiles and doing the rest on the fly has
always appealed to me too. In fact I thought this is what IIAB was doing. But
I now think that in order to render anything you need the 500+G database, which
Braddock and now Anish have put on the large rendering
