I think what you’re saying is that the Relief Line should be a RER-like service, where it only connects to major transit interchanges and destinations, similar to IF the Richmond Hill GO was made RER (15 min two way all day), had stops at Bloor and Eglinton, and had TTC fares?
There are certainly international examples we could look to (I am sure steve will be happy to pull up for us) where RER-like service turns into rapid-transit like stop-spacing when it approaches the downtown core, with stops every 800m-1km rather than every 2-3km. I am sure in situations where double-tracking is available, there are even express services that upon reaching the downtown core, by-passes all stations until they reach their Union-equivalent.
But I have a few thoughts on that.
First, stations are the most costly item in these transit mega-projects, especially when they are underground. I believe that those local stations would be cut for efficiencies, especially once Ford takes a look at the ridership numbers for a stop like Sherbourne and questions what's the point? After all, the downtown elites under Mayor John Tory thought that a 6km stop-spacing was appropriate for Scarborough, did they not?
Second, I doubt we have the foresight in this city/province to future-proof with a double-tracked line. Plus we are in efficiency-finding mode. This is an even easier item to cut than the local stations.
Third, even if the service accomplished the above with local and express stops, what would the frequency be like? Every 15 minutes as is generally considered as best-practice frequency for RER? The Relief Line as proposed was going to have 3-minute frequencies to meet the PPHD demands.
I guess this makes sense from a regional perspective, but it does make me wonder: If the Relief Line was built 50 years ago, would we be debating about an Express Relief Line vs second local subway line through downtown now?
We could answer that by looking at what is happening on the west. Remember, we already build a "Relief Line". It is called the University-Spadina Line.
I think that had we built the Relief Line 50 years, we would be looking towards investing in GO-RER within Toronto now. As evidenced by the demand of some neighbourhoods (like Weston) that aren't well serviced by subway lines, there is potential within the 416 for greater commuter rail integration.
But first, we need to build the necessary capacity on the Yonge Line (to enable the Richmond Hill extension), to intercept our trunk arterial bus routes on the east-end of the city in order to greatly reduce commuter times for Scarborough and North York residents, and to build a workable alternative to the Yonge Line to provide essential network redundancy.