Rocket busses are not a bad idea, and the TTC should consider operating more of them. But their cost is not next to nothing, they still have to buy the buses (and replace them sooner, and use more for a given demand level) and pay to operate them, and they will still get caught in traffic like any other bus, weather or not the word rocket is on them. And its not like the TTC has a good track record of managing bus lines either.
I say a network of lrt lines because they are planning to build them anyways, their frequency would not be limited by interlining them with the srt because not all of their vehicles would be funneled down that corridor, people do go to places other than the subway on transit.
My main objection to a subway is that it costs a lot of money for the area that it serves, if there is enough people on one then its not a problem. But their is nothing to even suggest that one would be needed, you can call low ridership projections a conspiracy all you want, but it doesn't change what is. The money saved from not building a subway can be used to start a transit line on another street, such as Lawrence for example.
Rocket buses are practically free compared to LRT lines, which require hundreds of millions, if not billions, of dollars of investment before a single streetcar can ply a route. Rocket buses can be had simply by shifting some existing regular buses to Rocket service...you don't even need to buy more buses or hire more drivers, as they can increase capacity and decrease travel time using the same number of vehicles. This is important to note because you insist these LRT lines are useful for random local service, which means high turnover along a route and the ability to serve more people with fewer vehicles. The TTC has a better track record with buses than with streetcars - try riding some of the many suburban bus routes that function well and you'll see that.
They are not going to build a network of LRT lines along streets that feed the SRT...there are no lines proposed for McCowan, Brimley, Midland, Lawrence, Ellesmere, Markham, etc. There may be an extension from STC to Malvern, but riders from that direction only supply a fraction of the SRT's total ridership, and the Morningside line would be a long trip to the subway that clearly would not be an improvement over a subway + Rocket bus combination. So, if it's not serving the SRT ridership base, and it would require transfers to get to Kennedy station, how exactly does the network you mention replace the SRT better than a [cheaper] subway extension would? LRT also does absolutely nothing for the STC area itself, which, if not already the biggest generator of SRT trips, will be the biggest generator once it's fully developed.
The area that a subway extension to STC serves is all of Scarborough north of Eglinton and east of Kennedy, as well as parts of Markham, a good 400,000 people. It's funny how you repeatedly cite subway technology as too expensive because ridership on the extension may not reach the theoretical capacity of the subway trains (if it did, how would someone at Warden get on?), yet you do not apply this same criteria to a series of LRT lines that may be running half empty but will cost, cumulatively, far beyond what the subway extension would, only they'll have smaller catchment areas, serve fewer people, not remove transfers, not reduce travel times as much as a subway extension, etc. The money saved by not building some of these LRT lines could build a subway extension and bring fantastic bus service to *every* rider in Scarborough, with money left over.