The obvious thing to do if ever to bolster the case for a true east-west subway south of Bloor, not just DRL, is whenever they're digging the tunnel bore for the DRL make it large enough such that it can accomodate a second set of tracks. These won't be service tracks for the initial DRL but actually rather preinstalled infrastructure for a Queen subway. Per this alignment conception the four innermost stations on both lines, say hypothetically: John/Wellington, Bay/Wellington, Church/Wellington and Sherbrourne/Front would be quad-tracked with two island platforms. The CBD Stn would also have two bay platforms connecting it to Union and King Stns. The eastbound tracks for both lines share the same platform area and vice-versa for the two westbound tracks. Beyond these points the DRL can wind its way through the innercity to connect to Bloor-Dufferin and Danforth-Pape (I choose Dufferin over Dundas West because its a busier interchange and denser area), while the Queen Street subway continues west along Wellington St to have stops at Cityplace, Fort York (Tecumseth, just west of Bathurst) and Strachan (King West Village) before entering the Weston-Galt. This leaves the stable neighbourhood of Queen West BIA unaffected by subway construction (expect for Queen/Peter where the DRL would channel through northwards) but the shortened 501 route length would make headways shorter, thus commutes faster.
However because this is an east-west Queen Line it turns west at Queen and Dufferin, with a stop prior at King/Atlantic. This is the stop for Liberty Villege and the CNE with underground streetcars extending from Exhibition Loop to terminate at this subway station. From Dufferin it runs west through Parkdale then elevated down the median of the Queensway (the existing streetcar ROW now housing the support columns for the guideway). After meeting a relocated Mimico GO Stn at Humber Loop the line terminates at Humber Bay Park one level up from a fare-paid streetcar loop west into southern Etobicoke. On the eastern front, the Queen Line cuts through King/Sumach (West Don Lands) before turning up and across Queen East to the Beaches. At Beech Avenue, a few blocks west of Neville Park Loop, the line veers northeastwards to terminate at Kingston Road and Victoria Park. Here it'd intercept the Kingston BRT which extends directly to Scarborough Town Ctr via UTSC and Centennial College.
I like this idea a lot, but I feel that Dufferin is far too east for the DRLs western Bloor connection. Dundas West offers connection to Bloor GO station and currently connections with the 504, and 505 make Dundas West a better option than Keele, Jane or Dufferin. A DRL west to Jane and Eglinton where the Jane LRT then continues north and a DRL west to Don Mills and Eglinton where the Don Mills LRT then continues north would be the best alignment IMO.
I also like your idea about the quad track, it recognizes the importance of the Queen corridor west of Dufferin and East of Broadview . This can work exceptionally well and cost effectively if Richmond and Adelaide are used in the alignment as TRZ from SkyscraperCity illustrates in this thread (
http://www.skyscrapercity.com/showthread.php?t=670156). This allows for the downtown section to be built cut and cover under Richmond and Adelaide and allows for a variety of alignments... Such as 2 eastbound tracks under Adelaide, 2 westbound under Richmond or the Local Queen line along Richmond and the Express DRL under Adelaide. This also allows for the DRL to run express only with stops at Dufferin/Broadview and Parkdale/Riverdale and then Bloor/Danforth, while the Queen Line runs local with stops at Parliment, Sumach/River, Broadview, Carlaw, Jones, Greenwood, Coxwell, and Woodbine in the east and Bathurst, Ossington, Dufferin, Lansdowne, Roncesvalles, Parkside, and Humber. The core 6 stations served by all trains would be Jarvis, Yonge (King-Queen), Bay, University (Osgoode-St Andrew), John, and Spadina.
The Express DRL assumes local service with stops at Roncesvalles, Bloor West, Dupont, St. Clair (Toronto West), Rogers, Eglinton, and Trethewey/Jane. With local stops in the east as well, you guys get the idea.