I have many experiences and observations with blue nights. Regarding blue night services, I do not see the need for any services on Bayview, Leslie, Warden (south of Sheppard), or Old Mill.
Martin Grove already has night service on its busiest part, which is the Rexdale community provided by 396 Wilson. You can tell it is busy by contrasting 46 Martin Grove and 191 Highway 27 Rocket.
Weston Road is something I would like to agree on. The day route, 89 Weston serves various high density communities, along with shops. In addition, 89 Weston is already busy at all times during the day, even the late evening. It even has Sunday early morning service before 8am. A solution I would find for this is an extension of the 384 Sheppard West; rather than terminating at Weston, it would continue southbound on Weston Rd to Bloor. This will allow for improved travel and reduced need of transfers between vehicles.
Markham Road is a corridor that also may deserve night service, but only as far north as Progress Avenue. St Clair East is a corridor I have not studied well, but it is surrounded by mid rises, and a growing transit usage. Related nearby is the Warden Avenue community south of St Clair, which I also observed is popular at many times during the day as well, and the Corporate Drive high density commuity, located west of Markham . Currently 102 Markham Road, which provides service to both St Clair East and Markham Rd is very popular, even during the evening. A solution is to provide a night service the starts from Warden & Danforth, travels north on Warden, east on St Clair, northeast on Kingston, north on Markham, west on Progress, west on Corporate Dr, south on Grangeway, to terminate at McCowan Rd (McCowan RT Stn) and looping back by going north on McCowan, and east on Consillium to route backwards. It combines day routes 69 Warden South, 102 Markham Road, and 134 Progress. The routings that are similar to 69 Warden South and 134 Progress would allow for efficient use of resources and improved transfering. This route would only require 3 buses and would have a reliable layover at the terminus. It would serve the various communities that aren't within a 15 minute walk, and improve safety and accessibility. Since it starts at Warden and Danforth rather than St Clair and Danforth, it allows those utilizing 300A to be able to transfer to this route, rather than this route be exclusive to 300B.