I think it's worth taking a look at the reports. The place I've found them most easily is unfortunately at the University of Waterloo. It's a three volume feasibility study, though the University of Toronto doesn't have the second, and most useful, volume. The Urban Affairs library probably has it.
I definitely wouldn't want to get distracted with all of these north-eastern and north-western extensions. The core section of route is definitely from about the Ex to Pape and Danforth.
Just to make it clear, the recommended first routing (and one I would more-or-less stick with) runs from Spadina and Front underground to Convention Centre at about John, then to Union Station. At Union, the station would go just south of the existing station, into the "moat". The additional platform presently under construction is already included in the preliminary design they did back in the eighties. From there, it would run diagonally under the Dominion Public Building and rail corridor to the south side of the rail corridor at about Yonge. It would then remain there until the Don. The corridor has enough empty space that there would be virtually no cost for this segment other than stations, which would be cheap and above-ground anyway, and the laying of track. The route from Yonge to the Don would literally be cheaper to build than a streetcar along Queens Quay. The Jarvis/Sherbourne station would serve the East Bayfront and St. Lawrence neighbourhood, while the Cherry stop would very effectively serve the West Donlands, east portion of the East Bayfrount, and the Port Lands. It could connect to the proposed Cherry streetcar. Beyond there, the recommended route shifted off the rail corridor to an underground alignment along Eastern Avenue, with the yard site at the present Toronto Film Studios, though that could be shifted. It would turn north at Pape, running up Pape until Danforth. This segment could definitely be re-examined, perhaps routing it along the rail corridor if room could be found. A stop at Queen and Pape is recommended to intercept streetcar passengers. It would also be an incredible catalyst for the revitalization of that area. I've actually even thought about running along Lakeshore east of the Don to Pape. It would seem to be possible to have an elevated line, if desired, and it could serve the eastern sections of the Port Lands, such as the new film studio, quite effectively, hastening their development. Pape and Gerrard is a great spot for a stop since the mall there could be easily re-developed. It was strongly recommended that the route end at Pape rather than Donlands, since that is a much busier subway station, is much more accessible by bus from the north, and is in an area where re-development is more desirable than at Donlands.
Don't be distracted by alternative routes along the Don Valley. The study examined them, thinking that they would be the cheapest, but finding out that they were even more expensive than Pape. There simply isn't enough room to add additional tracks in the valley, so they would have to tunnel. Add the cost of flood protection and the massive elevator/escalator at Broadview and it becomes quite impractical.
West of Spadina, the route would run along Front to Bathurst, then along the Front Street Extension corridor (already city-owned!) to the Exhibition. A stop at Bathurst (Fort York) would serve that major waterfront development area, while the Exhibition stop could potentially connect to that Waterfront LRT. I've been partial in the past to continuing to Roncesvalles and Queen, where a big streetcar terminal would be located, and underground up Roncesvalles to Dundas West. Lately, I've begun to consider the alternative recommended route up Dufferin from the Ex to Queen, and then north-west on the rail corridor.
North of Danforth (and Bloor), the route was only very vaguely discussed in the study, though in the east end an extension to Eglinton and Don Mills was examined, with intermediate stops at Cosburn and Thorncliffe Park. You could add an extra stop in there at Flemingdon Park, I think. The report considered running the route elevated along Overlea and Don Mills, though that was with Skytrain vehicles rather than the much heavier subway cars. Nevertheless, it should still be possible. It also wasn't able to determine whether the Leaside Bridge could handle the extra weight, or if a new and much more expensive bridge would have to be built.
I also consider extensions north of Eglinton to be quite useful, serving Don Mills in particular and relieving the circuitous Lawrence bus route.
It's been my life-long goal ever since I wrote that article what must be almost a decade ago to revive discussion of the DRL. I've tried every possible way, but I wish you good luck.