That is exciting! Open and well-documented FPGAs are definitely useful and very interesting to have in a device. Have you looked into OpenPiton [0], PULP [1], BOOM [2], or lowRISC [3]? While I'm hopeful that you find these projects personally interesting, I'm also looking forward to eventually see them in devices. Sorry for not listing any open POWER CPU/SoC projects as I'm not aware of any. Please share if you know any.
[0] https://github.com/PrincetonUniversity/openpiton [1] https://github.com/pulp-platform [2] https://github.com/riscv-boom/riscv-boom [3] https://www.lowrisc.org/