Steve Munro has talked about the probable need for a second GO station at Bathurst for the Lakeshore line to relieve congestion at Union given all of the ST/RER plans. There's a case to be made for having a spur of DRL run south to this station, so that the Lakeshore line passengers would have a subway connection to the central business district. Munro has alluded to this as well. I really do think all of these transit/transportation plans need to be considered together: ST, DRL, and yes, Gardiner removal/burial.
If we ran the DRL under Queen/Richmond and had a spur jut south at Bathurst to a new GO platform/station around Bathurst and Front, why wouldn't we finally complete the Front St. Extension west of Bathurst (a longstanding city plan), the purpose of which would be to provide an on/off ramp to the Gardiner. My thinking is, put the Gardiner in the same ditch as the DRL. Would it be that much more expensive than trying to dig another train platform and track set under Union, throwing a billion at the Gardiner Hybrid, and spending tens of millions trying to spruce up the land under the elevated Gardiner? Yes, it's more costly in the short run, but you open up land for development along Lakeshore, beautify Lakeshore Boulevard, run traffic underground, and create a more complete transit loop.
The ideal would be to have the western stretch of ST between Union and Bloor have stations at Spadina and Front and Queen and Dufferin, a DRL running to Dufferin and Queen (for ST transfer) with a spur running south of Queen and Bathurst to a station at Bathurst and Front (with transfer to GO). I'd also advocate to have DRL stations for the Entertainment District (Queen and Spadina), Bathurst and Queen, and either Queen and Ossington/Shaw or Trinity Bellwoods (or both?). As mentioned before, if the DRL runs under Queen, use the same streetcars in the tunnel as above ground for ease of transfer and cost savings (there are stations roughed in for streetcars beneath Queen and Osgoode stations). If we use a subway, put it under Richmond, so that the streetcar tracks on Queen remain intact (not just to relieve transit chaos during construction, but because we'll need those streetcars. They provide more stops than the DRL and would handle commuter overflow at rush periods).
I realize the Gardiner burial idea is a non-starter for some. In that case, leave it out. I'd still do all of these other projects. A Front Street Extension that connects to the existing west Gardiner would allow us to achieve the European model of having a regional train station (for Lakeshore GO) and parking at the edge of the downtown (where cars come off the Gardiner), with the ability to access rapid transit into the downtown. Cities such as York in England use parking garages combined with shuttles into the city. Really, having this additional ramp from the Gardiner at Front St. with access to transit would make the rest of the Gardiner largely unnecessary. It could probably be removed without replacement. If we need an expressway connection to the DVP, put it underground with a toll charge. Tolls are the standard in most major cities with downtown expressways. I realize that for many on here, tunneling the Gardiner, with or without tolls, is a separate discussion, same with removing the Gardiner. Fine, but all transportation flows should be considered together for the quality of life not just of drivers and transit passengers, but the impact on pedestrians at street level.