With Don Mills station becoming an important link/transfer-point, the DRL should start here (so it is connected to the Shepperd/Finch LRT and the Shepperd subway), go south via Pape through the financial district and king west district and come back north via Dundas West and connect to Jane Street, where it can connect to the future Jane LRT.
With the plan for Jane LRT to connect with Finch LRT, the connection of Jane LRT to the so-called 'downtown relief line' (as per my point above) would enable one massive transit loop covering outer-Toronto via the downtown. This would greatly improve transport in any direction in the city of Toronto, and would particularly help lower-income outer-ring suburbs and highly-dense inner-city suburbs.
The city of Toronto would then have a one large seamless LRT line covering the north (Shepperd linked in with Finch), a large seamless line covering central Toronto (Eglinton crosstown), the existing south subway line (Bloor-Danforth) and two loop lines - the existing inner Yonge-University-Spadina subway and the new Don Mills-Downtown-Jane line.