P-p-p-p-plase lets get on track here. One needs some onboard DC/DC and a FPGA. Anything else is just a burden that won't benefit the design goal.
The addition of any ASIC CPU will require lot's of scarce I/O on the FPGA, more power, more mess circuit board routing, more debugging, complicated sourcing, larger FPGA which cost more and is harder to source.. and harder to solder, additional RAM, boot ROM, etc. Just because you can do something doesn't mean it's suitable.