NVMe wouldn't give you the best latency, but a 16x PCIe card loaded with DRAM and addressable as a scratch disk doesn't sound bananas. I wonder why Apple didn't market something like that as a first party solution.
Let’s lie to OS and tell it that this memory is actually a disk. Then, it will lie to the programs, and tell them that that disk is actually memory.
That said, it isn't the bet I'd make if I was tasked with purchasing for a company. I'd get the studios in a reasonably high config and then sell them every 2-3 years and replace with newer model. You'd pass the pro's in perf pretty readily from CPU bumps alone and likely recoupe a lot of your investment.