There's no such command, but it wouldn't be hard to create one if you know a little emacs lisp and look at other magit-branch-* commands and the SO answers you mentioned. If you do, then please submit a pull-request.
There are lots of ways to do this. One way is to put system dependent stuff in a file machine.el where "machine" is what (system-name) outputs. I then put
(require (intern (system-name)) nil 'noerror)
in my init.el and keep everything in the same GitHub repo.
Same issues. Unfortunately, projectile switch project doesnt work for nested projectile projects. Or I cant get it to work,
One solution is to use helm-projectile-ag for example but prefix it
eg C-u M-x helm-projectile-ag
you are prompted for options so add "-u" (the ag flag to ignore .gitignore) and it will recursively search outside of the laws ...