^ Seems like a moot point since 1) based on everything I've read there is no appetite to detach/decouple Yonge and University (and some have said here it can't practically be done) 2) it's hard enough to see when a DRL might reach Eglinton, never mind north of it, so planning all that and getting it funded and built within a small enough time frame to pacify York Region is very optimistic at best, and 3) to continue sounding like a broken record, Yonge has a completed E.A. with at least three governments willing to fund it the next time transit money is thrown around, while the DRL has close to nothing.
Yonge will happen, and there is no getting around that.
1) The decoupling is just a thing I added, the Richmond Hill Subway proposal can happen without that.
2) It's been stated several times that the Yonge extension shouldn't happen before the DRL (stated by the TTC, stated by Metrolinx, and even stated by York Region themselves), otherwise the Yonge line will be overloaded. This makes the "state of readiness" of the Yonge extension borderline irrelevant, because it's in a holding pattern until the DRL is figured out. The fact that it has an EA and stuff ready is great, but I believe there is time to at least study the merit of alternative proposals, especially when it's directly linked to the DRL, which is going to be extensively studied anyway.
Gweed. I notice your map includes an extension of the yonge line up to Steeles. I guess that section won't place any added burdon on the yonge line, or is that an acceptable cost to accommodate development on North yonge within Toronto's borders?
What your plan will not provide is a transportation link between north York centre and Richmond Hill centre as envisioned in places to grow. I happen to live at yonge and steeles and can say with all honesty that if I'm going shopping I'm more likely to travel north to Richmond Hill than south to North York or Toronto. for dining and entertainment I am more likely to go south.
Our nodal growth strategy is about creating urban centres throughout the region. Not linking two adjoining centres, North York and RH centre is effectively isolating them.
I included it as a dashed "Phase 2", much like I included a Sheppard West extension in Phase 2. I added that for a couple of reasons: 1) Because, like you stated, it won't add any extra burden to the Yonge line. 2) It will support the northward extension of NYCC along the Yonge corridor (it's already stretching north of Finch), and 3) It will allow VIVA to build a proper terminal at Steeles, with an easier transfer to the subway.
As for the connection from NYCC to RHC, I've stated previously (although it's not shown on the map, so I probably should add that) that a VIVA BRT along Yonge would be more than enough to handle the demand. Under the current subway scheme, the Yonge BRT coming from north of Highway 7 will terminate at RHC. If the Richmond Hill Subway is built, that BRT can continue south along Yonge to either Finch or Steeles (wherever the Yonge terminus may be).
This way, riders have two options if they're riding southbound on Yonge at say 16th Ave: Transfer to the subway at RHC, or stay on the VIVA bus and go to Finch/Steeles. If most people are bound for downtown, they will probably choose the former, as it will be moderately faster and less crowded. People bound for NYCC will likely choose the latter. Point is they're both good, rapid transit options.
Another point to raise is that there's no reason why the subway needs to stop at RHC. Since this would be effectively replacing the Richmond Hill GO line, York Region could choose to cough up a little bit extra (or hey, Toronto could pitch in a bit for some of the surface section inside of Toronto, freeing up funds to push it further north), and extend the subway to 16th Ave or Major Mac. Since it would be a surface extension replacing an existing rail line that has grade-separations in place already for most of it's length, it would be a pretty inexpensive stretch of subway to build.