I was waiting to see if someone with definitive information could help you but since nobody has stepped forward, I can offer my advice, which is based, at least in part, on hunches.
I wasn't aware that if you had the correct NVMe driver that the Thunderbolt driver would just pick that up and it would work. However, in looking and the Sonnet and AKiTiO websites, that may indeed be the case. So ...
Is there any reason why you can't use High Sierra? It has a NVMe driver that may work in your case.
If you can't use High Sierra, prior to High Sierra, OSX has had a NVMe driver since late Yosemite, but it wasn't plug-and-play so that it wouldn't recognize most (all?) non-Apple SSD's. People who have Hackintoshes have been able to use a patch called "HackrNVMeFamily" and a configuration file customized to the specific SSD being used to make it work. The issue is that the work required is not trivial and a cursory search on the Internet turned up two cases where people who had the P3600 weren't able to get it to work (or they didn't report back if it did).
I would try installing High Sierra to an external disk and see if it can recognize the P3600. Even if you don't want to use High Sierra you still might want to do this - if it can't recognize the P3600, my guess is that going the arduous route of trying HackrNVMeFamily won't work as well.