NUWATC Newcomer

Here is the senario:
Heavy aircraft in the tower pattern doing multiple touch and goes. Continuous stream of GCA aircraft on final approach.

Here is the question:
Can i use visual seperation by calling the final controller, making a traffic call,have the final controller wait for his aircraft to report my aircraft in sight, then have the final controller tell his aircraft on GCA final to maintain visual sep, caution wake turbulance? I realy dont think you can. you are adjusting the aircrafts flight path with ever turn you give him on a PAR and if it is some monitiored instrument approach the aircraft cant deviate from the published proceedure to maintain visual. So then in that case do i need the approprite mileage behind the heavy? And if i do need mileage who is responsible, radar, or tower. And does that change if i have a certified radar display in the tower or not? Chew on that for a while, let me know what you guys come up with.