Problem is, to stop chat from working in the normal box, you have to stop it all together and take over the commands.
We pride ourselves on the ability to not break other chat mods/commands.
The emoticon chat box has been done before from Facepunch.
If I remember correctly, it broke every mod that used chat based commands, including ULX, Citrus, NewAdmin, many others.
New updates to Gmod might have better chat functions, but I really doubt any that would prevent that.