this is IMPECCABLE work i was on the edge of my seat the whole time

i do want to mention that you can get further with the <( $(cat custom-bashrc) ) approach if you just add more quotes x3

; ssh -t linode "bash --rcfile <( echo '""$(cat custom-bashrc)""' )"
linode-static:~$

but it breaks again as soon as you do anything complicated (e.g. my real bashrc):

; ssh -t linode "bash --rcfile <( echo '""$(cat .bashrc)""' )"
zsh:98: unmatched '
zsh:98: parse error near `<( echo 'if [ -n "$B...'
Connection to 50.116.47.176 closed.

ok here is a version that doesn't require smuggling environment variables and works for arbitrary numbers of files and arbitrarily weird syntax

$ (x=$(cat .bashrc); ssh -t linode "$(declare -p x)"'; exec bash --rcfile <(echo "$x")')

this also does not set any variables in your parent shell, because that's stateful and we don't want to be stateful

extended to vim alias: ssh -t -o RemoteCommand="$(ssescape x); $(ssescape y);"'exec bash --rcfile <(echo "$x"; echo "alias vim='\''vim -u <(echo "$y")'\''"; )' "$@"

This reminds me of

https://github.com/sineemore/backpack

There are many forks with very minor changes if you poke around github.