A couple points. First you could use surface mount ICs and fit a whole lot more circuitry onto one board. Soldering is harder but it should be better in every other way.

Second. The register file could be implemented with far fewer chips if only a single output was used. The A and B register select bits would need to go through a quad 2-1 multiplexor and the output would need to be latched for either A or B and some sequencing logic added to make it work. In other words it would take 2 cycles to read from both A and B operands.

Oh, and don't forget that in RISC-V register 0 is always read as zero so no actual storage is needed for that one.