For admins, I believe the ability to see private messages between players(excluding admins) would be beneficial to administrators.
I was afk recently while playing on Beast_Build, all was quiet, or so I thought.
Suddenly I see from one guy "1p <player> they'd probably ban us"
Well, needless to say, they missed hitting shift.
I went on alert. Nothing else happened, but, I came up with this idea.
Logging of and ability of admins to see !p/psay communication between players. (I've not checked logs lately, does this happen already? Probably)
Two ULX_Cvars, one server side, one client side.
Both on by default - Server cvar would set "allow admins to see private"
Client side would set "allow me to see private" (I could see some admins wanting to temporarily disable)
By default, I don't recommend admins be able to see other admins private chats (though, perhaps superadmins could, again, ability to disable locally)
No extra indication would appear when seeing "Player1 to Player2: <blah>" on the players side.
Perhaps a color change if the server cvar was on might be only indication. Dark blue = on, light blue = off.