Digium phones 'msgs' and top red LED

It’s similar to this question which I saw @BlazeStudios answered - mine is a slightly different question, I keep thinking of how I can simplest explain it:

Maybe this:

Two (hard) phones which I want to be totally normal phones - except the MWI indicator and the visual voicemail on the second phone should link to the voicemail mailbox on the first. Doable?!

Thanks!!

EDIT: Is it just as simple as changing ‘mailbox @ device?’ in the extension settings??
EDIT2: The only thing that gives me pause is I use DPMA not EPM…and here there’s talk of editing a basefile in EPM which obviously I can’t do…