Being from Etobicoke, and not Scarborough, I'm not precious and don't oppose the concept of across the platform transfer. So I'm quite happy if people change vehicles at Mount Dennis. But I suspect that it will be decades before the Ontario Line (whatever it becomes) will be ready to push west from Exhibition. And the marketability of a through ride from Pearson to Eglinton east of Mount Dennis seems too desirable to pass up. So, keep Eglinton West as LRT for now, but build it with Ontario Line clearance specs so that it can be converted some day when the Ontario Line reaches Mount Dennis.But there's more. Sauga has done some heavy lifting with Transitway grade-separation between Renforth and Hurontario. This could lead into that (one day), just needs a proper connection to Sq One. Also one day, a N/S subway of the same system running from Kipling to Pearson - this is integral to the vision and the reason I posted. It'd be an integrated network of smaller automated subways serving 427 corridor-East/West Mall, Pearson, Eg West, and Sauga. Be a bent cross shape, about 30km, four services: Sq One-Kipling, Sq One-Black Ck, Kipling-Pearson, Pearson-Black Ck. Drawbacks, yes. But huge benefit.
If the OL ends up being something other than vanilla TTC subway, perhaps it and the Crosstown spec's ought to converge somehow, so that Crosstown can be upgraded to the same vehicle parameters some day. I continue to wonder if Eglinton will exceed three-LRV tram capacity sooner than we predict.
I definitely like your idea of integrating with the Mississauga busway. I can see an eventual interleaved line that has service Pearson to MCC, Pearson to the east, and MCC to the east. A transfer for some at Mount Dennis doesn't strike me as a showstopper in that.