I'd assume extending the account migration to include blocks, filters, avatar, etc. has been considered, but I can't find a general account migration UX discussion in the GitHub issues.
Losing some followers when moving servers, however, is pretty much inevitable. All the protocol can do is ask them to move - some will refuse due to server blocks or other reasons. Steve kept 97% which is waaay above average. A way to show a list of the failed ones would indeed be good.