I'd definitely be considering a few. Been tinkering with an R606 I purchased from bitshopper, its pretty deadly. I tried it on my old slush account, not making much returns there; however, to be expected. So I've put the unit on at http://pool-btc.ga mining solo BVG, its smashes those blocks like an absolute beast, some really clever gadgetry going on, hardware was always my issue back in the day, the S3's I was running were bought second hand, so the r606 coupled with a lower difficulty coin - I've never seen anything like it.

I've been deploying some mining contracts through http://miningrigrentals.com, and the r606 (solo-http://pool-btc.ga) is outmatching an S9 (prop) http://persianmine.net, though this may be due to the difficulty settings used by the pools on the coins I am targeting (mainly BVG).

I like the r606 form factor, although for a stack something like those FPGA cards in a ATX / mini-ATX case would look pretty good, if cooling wasn't an issue.

I would suggest that keeping the Rpi away from the assembly would be a good idea at least for offering a scalable product, I think issues experienced by R606 users may be associated with RAM, the headless Rpi 4 is running at least one r606 very well, i don't really know enough about what each component in that configuration is doing, but an FPGA style offering to be paired with a proliant system would probably spark alot of interest from bigger commercial contractors.

From the RnD off this device i've bitten the bullet and building a cryptopool at http://moonpool.io

Keep us posted !