A workable option might be to get an external GPU enclosure and a full desktop GPU, and connect via FireWire , as well as upgrade to 64gb RAM in your current laptop (if the RAM isn't soldered in, ofc). This does kinda kill the portability, but it sounds like this is a workstation anyways, so might be fine.
Unsurpringly, it seems this functionality went away with the M-series chipset. So I guess we just wait for the $4500 Apple-silicon 2060ti-equivalent in a year or two.