Ideally, yes. This would make the idea a little more attractive to me as currently I gain nothing in terms of time over before, even if everything is working perfectly. The current plan may work for those less keen or less able to change trains, but if I’m going from Cambridge to Brighton or Gatwick then I’d still plan on a non-stopper, Victoria line, fast train from Victoria.
However, the fact that in the peaks most services start/terminate at Kings Lynn, and call at Waterbeach, restricts everything to 4 carriages (unless we start putting splittable trains through the core). Even if the platform lengthening work ever gets done (!) it will still only be 8 cars. Plus there is the long single line section, which is very time-sensitive. So I don’t really see how this could work