The fpga here is already programmed to be an SOC. The skillset would just be embedded programming for a microcontroller with very little memory. Plus all the isolation features of this particular device.

"While the reference FPGA ships with a 32-bit RISC-V CPU running at 100MHz, it can be reconfigured to emulate a wide range of retro-CPUs, from the 6502 to the Z-80..."

https://www.crowdsupply.com/sutajio-kosagi/precursor

If you don't care about all the security stuff, I think you would enjoy an ESP32 or a Teensy a lot more. Both have some 3rd party guidance on using Rust with them. And both have more memory and better docs.