You want your shell stuff to work the same way even when you use a
different shell, or even a different box. Right?

If you use poshinit (Portable Shell Initialization), you can attain at
least most of what you desire, perhaps even all. You can log out of Bash
and log in with Zsh (or vice versa) - and your aliases/exports/functions
will continue to work as before.

It gets better - if someday you need to use a different box with a
different OS, you can get your shell to work your 'normal' way in a
jiffy. Just save your $HOME/.shell directory on your primary box, and
paste it over your second box's $HOME/.shell (after running poshinit
setup script on the second box). The second box need not be the same
operating system - poshinit works across FreeBSD / Linux / Cygwin.

WWW: https://github.com/bourne-again/poshinit