The problem with offering participants direction of investments is participants themselves. As a whole, they make poor investment decisions and exhibit poor timing. So that is just another reason why Bitcoin and 401(k) plans don’t match.
No regulation and too much volatility make crypto a hard no for me. Based on participant experiences of the past, my concern is that too many participants will make investment decisions that are too rash and they will lock in losses when there is a huge downswing in Crypto.