Thanks, everyone.
My thoughts are to get the tyre physics done without delays, without looking for perfection, just to get something out there that feels good and has a physical basis. The current public version tyre physics system uses some made-up force curves that are somewhat like real ones, and tuned to give reasonable output values, but they are not produced from an actual physical theory. The lateral and longitudinal forces are combined in a way that also is not based on physics, and was simply constructed to give a reasonable feeling.
In the new tyre physics, the forces are produced from code that follows physical laws, instead of looking up the forces from a curve. Lateral and longitudinal forces are output naturally, rather than being 'combined' in an arbitrary way.
There are assumptions involved, but they are 'known' assumptions that are there for a reason and can be improved upon in the future.
Anyway, I hope to continue with the work pace I have been doing in recent times, and don't see why this can't be the case.