I've actually done this before.
Approach: "Freighter 741, Uhh, you've got a 100kt overtake on an arriving EMB-170, can you slow to minimum approach?"
Me: "Uhh...is that the guy I'm showing on TCAS,10NM in front of me?"
Approach: "Uhhh, yeah...why?"
Me: "How much separation do you need? I'll maintain a mile more than that and if I get to close just send me around."
Approach: "Alright...that's a new one, sure, I'll let you know if you get too close. I need XX amount of separation."
Worked great, I just kept the dot outside of the appropriate ring, and followed him in on the ILS. Before I switched to tower the guy says, "that was kind of neat, never seen that before."
Please tell me you're kidding...