Not quite real time, but the usual XDCR speeds (which by the way is amazingly fast, thanks) with the acceptable network latency to get the eventually catch up is just fine (say few minutes to even an hour or two may be reasonable --basically proportional to the Writes volume on either end).
Another simplification I can offer in my requirement is that – same docs won’t be dirtied on both clusters during same time windows, so conflict resolution is something we don’t need to solve for.
-AP