It should be.
I still say extend the BD to STC and then stop at Skeppard/Markham with provision to go north at a future date from day one. I said this long before TC surface.
You extend the Eglinton line to the east.
I have some ideas regarding the SRT conversion. For starters build a brand new Kennedy subway station underground and reconfigure the B-D tracks to run through it instead. This will allow for easier turning radius to get northeast. The existing E-W Kennedy could then become useful ROW for the Eglinton-Crosstown LRT/Premetro, freeing up that line to operate exclusively along that corridor.
To Scarborough Centre:
We could then expand on the existing N-S section of the SRT ROW and existing
Lawrence East Stn. I'm sure modifying the existing infrastructure would be cheaper than building everything from scratch. North of Lawrence around midblock the line then veers underneath the Stoufville GO Line and makes a stop directly at
Ellesmere/Midland. Cutting through the industrial properties on the northeast side, the line eventually merges with the existing elevated ROW (which could inevitably house express BRT/LRT from Sheppard), running beneath it. A
Brimley/Triton stop is optional.
Future Extension into Malvern:
Scarborough Centre Stn shifts to the east with exits now out to McCowan Rd and the GO bus terminal/mall entrance. The TTC bus terminal could remain as is or too be relocated eastwards. McCowan Stn eliminated.
Bellamy,
Markham Stns easy walking distance north of Ellesmere. Line would then proceed to cut through the parklands east of Markham Rd at-grade northeasternly towards
Progress Centennial College. Then runs parallel to the 401 before burying under Neilson to Malvern TC terminus, stopping at
Sheppard East en route.
Malvern TC could essentially become a transit hub offering excursions to the Zoo, UTSC, Durham, and Markham/Cornell.
This could work either as light rail or heavy rail rapid transit, though the latter would reduce overall no. of transfers thus travel times.