At the moment read transactions that don't acquire topology lock will be forcibly rolled back on topology change as read tx can be in fly while topology being change.
This is done to prevent having active transaction with stale snapshots on new topology in cases of TX coordinator or Near node were lost.
It would be nice to remap it somehow until they locked a topology or at least throw some meaningful exception to user.
For example, it is possible to obtain a new "write" mvcc version from the new coordinator and use this version for all further writes while using "old" version for reads. In this case we need to change visibility rules a little: "old" version should see "own" updates made by "new" "write" version.