I did try that but it just runs 'set -o vi' and exits. He shows using it to launch a multiplexer... I suppose it's an alternative to 'ssh -c command'. I tried to figure out a way to invoke 'set' followed by the remote user's $SHELL but couldn't figure it out. I'll keep fiddling; thanks for your reply
All of the single-character shell options documented in the description of the set builtin command, including -o, can be used as options when the shell is invoked.
So set RemoteCommand to something like /bin/bash -o vi