Ahhh, ok now I see what you're getting at. The terms "simulcast" and "multicast" are often confused, even by the experts or industry terminology usage. One refers to broadcasting an identical transmission on identical frequencies at the same time, the other refers to broadcasting an identical transmission on different frequencies at the same time. All you're looking for is a way to group X amount of channels/frequencies together, then have the scanner decide which has the strongest signal anytime a transmission is received on those grouped frequencies, and to have it lock onto that dominant signal while ignoring the rest. There are commercial radios that already have such a feature, so I suppose it would be feasible to add to a scanner.
The NYS Thruway Authority uses that concept in their mobile radios, where the repeater sites alternate the output between two frequencies to provide overlapping coverage and reduce same-frequency capture effect interference. The radios measure and compare the signal strength between the two output frequencies, and will lock on whichever is the strongest at any given time. Sounds like that's what you'd like scanners to be able to do.