I think we should put BRT in the Eglinton corridor. It was brought up a few times at council about the justification for the Eglinton West LRT, and staff would shy away from the ridership numbers, and insist the extension was for "network completeness" and to make a connection to the airport. The current Crosstown terminates at a (future) GO/SmartTrack station, which presumably would be a UP Express station, and therefore a faster connection to the airport.
SmartTrack should have been a plan to integrate all GO lines in Toronto, by increasing train frequency (already in the works), adding some stations (such as those proposed), improving connections with TTC stations, and integrating fares with the TTC (the big missing piece in the plan).
BRT could be designed with the necessary grading and curves so that it could be converted to LRT in the future. As well it could use Mississauga's (already under construction) infrastructure at Renforth Gateway, and a combined route up to the airport. Therefore both MiWay and TTC could send buses up to the Airport. I think Mississauga would be much more willing to pay for this infrastructure. Overall this would be cheaper, and for the same cost as the LRT, you might also be able to build BRT from Eglinton/Weston up Jane to Finch, another busy route, and good connection to the Finch West LRT.
Otherwise funds are better spent on things like the DRL, or waterfront transit, which even the local councilor even suggested.