> still needs manufacturer supplied toolchain for the rest of the steps

This still kills the desired properties of the system. You need open source tools end-to-end, all the way down to the place-and-route system. A backdoor can be inserted at any point otherwise.

Stepping away from the current state of things, competition in the FPGA space still relies heavily on patents and trade secrets. Until that changes, the proposed approach isn't viable.

I wonder if Xilinx or Altera will ever consider this market space interesting enough to pursue. Unfortunately, my gut says no.