So I got thinking that I could likely do this with IS.
I could make a global macro on G1, that toggles this echoing of "1" to instance 1 of the game, and I'd never see it in instance 2, or 3, etc.
Not too sure if this is doable at the script level; my limited knowledge of your scripting language (ie, tearing open the .is files) hasn't revealed a repeat or similar option.
Any hints on how I would approach this? Just a direction, and maybe some documentation should be enough, I hope.

BTW, this ISBoxer Toolkit looks really promising, keep up the awesome work!
(Hmm, maybe I should examine this Key Maps mod.)