Sorry about grammer , Im on phone and its glitching...We already deal with RPT on a regular basis, sometimes with 3 in or inbound into the circuit at a time, plus several chinese students and a few others in training areas, flying over head, the tourist seaplane and the meat bomber etc etc In a very busy circuit area and the speed differential even without anyone helping ( we are non CTA) us is the least of or issues... the issues are radio congestion from sharing with Taree and lack of a taxiway to clear the runway and keep the circuit flowing...so some times downwind ends up being extended 5-7 miles to the North... When its real busy the RPT guys will stay at 2500 and join mid to late down wind at a bit of a 45 of they make a strange base turn that sort of indicates they might have done a variation of a downwind out wider ...they might be 2 miles wider and do a big sweeping base turn... apparently this offers better visibility then merging at 45 ... judging by the alarms, i think it also stops their TCAS going of its brain as much as well.
I can honestly say after flying over 120 hours of my total hours just in our local circuit the RPT speed differential does not cause much problem if any for us. So I would imagine in CTA with highly trained professionals maintaining separation as their primary job, and monitoring speeds, its not going to be an issue... The issue in my mind would be some gumbie landing and then sitting on the runway causing a stack up behind him/her, or someone not following the headings, altitudes and speeds they have been assigned, or lining up for the wrong runway in a parallel runway situation. Form my experience which isnt much, through CTA with others, if you say unfamiliar they are super helpful, even to the point of telling you exactly what to look for .