But I have to admit, that I ended up buying my own IPv6 block from a local ISP and tunnel to them. They have great interconnections, so bandwidth is not an issue, and latency penalty is less then 2 ms an average.
TLDR: Turn the frequency of your RA-s waay up (3-5s) and their valid lifecycle way down (10-30s). There's still gonna be a hickup, but it should be tolerable.
But I have to admit, that I ended up buying my own IPv6 block from a local ISP and tunnel to them. They have great interconnections, so bandwidth is not an issue, and latency penalty is less then 2 ms an average.