I noticed all the stores around here stopped carrying unblended cypress mulch also. I have no idea why, but all they sell (5-6 different stores) is now some blended kind. Where do you buy your coconut husk bricks? I'm going to have to start using that for my BRB to keep up proper humidity since I'm almost out of cypress mulch.
OP, like everyone else has said, the biggest problem will be keeping proper maintenance measures for the stones/marbles. I could see that be very tiring to clean after awhile.