One of our biggest disappointments: we had plans to add a way to enforce strong consistency leveraging (IIRC) something akin to multi-paxos, but couldn't get it to work.
The engineering exodus around that time sorta killed the project though, and we never were able to do the big follow-up work to make it really shine.
(Disclaimer: Former Basho Principal Engineer, primary author of strong consistency work, lead riak_core dev from 2011-2015)
I think another 18 months would have been enough too. But it just wasn't the right environment after the hostile take-over / leadership transition.
I apologise if we do eventually cut it. Having worked through the code when chasing unstable tests, I developed an appreciation for the quality of the work.