Edit: There's a lot to like here, but a lot that is confusing. An FPGA based version of PicoPV32 could be really secure. Your attack vector would be the FPGA vendor doing something at the hardware level (hard to pull off), or the toolchain being compromised.
But what FPGA it is matters, also what toolchain they are using to programme the FPGA (yosys is not mentioned ...). The whole "locked down" FPGA bitstream sounds very fishy as well.
PicoRV32 does fit into Lattice FPGAs and they are fully reverse-engineered and supported by yosys.
Edit: There's a lot to like here, but a lot that is confusing. An FPGA based version of PicoPV32 could be really secure. Your attack vector would be the FPGA vendor doing something at the hardware level (hard to pull off), or the toolchain being compromised.
But what FPGA it is matters, also what toolchain they are using to programme the FPGA (yosys is not mentioned ...). The whole "locked down" FPGA bitstream sounds very fishy as well.
PicoRV32 does fit into Lattice FPGAs and they are fully reverse-engineered and supported by yosys.