Most airfields these days have an ATM (aerodrome traffic monitor), if it looks as though a pilot is going to turn too soon or be too near to the aircraft of a higher vortex category, I use it to tell them so.
Equally, if an aircraft is downwind and No.2 to the same aircraft, I will use the ATM to tell them that their current track distance exceeds the vortex wake recommendations, (bearing in mind that they may, of course, turn in early).
I know its not one the listed uses for an ATM, perhaps it should be, but I've done it with SRG present, and not had any negative comment.