I don’t have a specific project in mind just yet, still got my feelers out. I have some assembly and Verilog experience, but I’m still a little green. I’ve ordered two books on risc-v, one on the architecture and one on the assembly language. The SiFive website has a portal to design your own custom cores for their processor, which seems neat. I’m still in the thought experiment phase right now, no hard ideas. My plan is to study the risc-v implementation, find a niche that would benefit from its ISA, design a custom core, develop the hardware on the fpga, and possibly make a prototype pcb. Most likely I won’t be able to afford having the custom core manufactured, so I will have it in the design but use the standard core for the real thing. Also, since you had such a reaction to the mention of Arduino, from now on I am going to end all my replies to your posts with the word Arduino 
Arduino