You want some sort of notification system? Not sure how that would work. Be more specific in your suggestions please.
That is what I missed in my suggestion.
Say, you want to mention a player(s) in your message. All the need would be to type "@REFERRAL_ID" in the text e.g. "Shout out @13 @69 @7". A final message would include mentioned players' colours e.g. "Shout out
Funtastic_Power Mike Treba". The notification can be any of GTA SA sounds playing for a referenced player (and a textdraw somewhere at the bottom saying "@REFERRER_ID has mentioned you in their message").