How to change key mapping behavior of macvim
I am an idiot...

I can just map the special characters...

imap Å &lt;ESC&gt;&lt;S-a&gt;
imap ˆ &lt;ESC&gt;&lt;S-i&gt;


Problem solved.

That said, apparently if you have macvim gui, you can use set macmeta in your vimrc and then do things like imap &lt;S-M-a&gt; &lt;ESC&gt;&lt;S-a&gt; which will work in theory, but I prefer to work in terminal and unfortunately macmeta is not available in terminal macvim