There are 36 emotes (which can be seen and understood by the opposite faction) in the game you could just make an emote to letters and numbers addon. It would be much easier than having people on the internet learn to read chain heal language

Do note, however, that written communication with the opposite faction by circumventing the already in place barriers is against the ToS. I had a GM notify me while I was working on an addon way back when the obfuscation of written text was reversible.

I like your creativity though...you might look into some of the grid languages used by PoWs. While a bit obscure they can be understood by people who know they are letters or words, and most were based off 5 or 9 point grids.