The only thing you've said is why given our current setup it wouldn't be possible, mainly how the trains don't short turn outside of rush hour, but just because they don't, doesn't mean they can't.
This is a place to discuss ideas for public transit, whether or not something is confirmed or not doesn't really matter all too much. We discuss what we want to happen, and we discuss why that thing we want to happen isn't possible. Sure at some point you have to draw the line between future proposals and absolute fantasy where we have subways running every single street 300m apart, but this isn't one of those cases. You haven't actually backed up why this isn't possible or why this is a bad idea, you just said "the current government isn't planning this therefore its not worth discussing". I'm sorry but no western extension of the Sheppard Line is currently planned, and any discussion of interlining with Line 1 is basically on the same level of fantasy as extending it to Sheppard West in the first place.
You don't care what other cities do with their systems? That's a shame. You're basically saying that you think the way Toronto does things is absolutely ideal there is no room for improvement or to learn from other cities to maybe make our systems better. I know you probably don't mean this, but the reality is that we should be looking at what other cities are doing and observe and see where their style of construction can benefit what we're doing. In Montreal, many of their interchanges are cross platform, meaning that if you want to switch to another line, all you have to do is walk across the platform. Perhaps this is something that Toronto can learn from so that we can improve our transfer stations and not have another St. George Station?
Vancouver is building their system with smaller trains and are elevating their system more. This allowed Vancouver to build a system that is bigger than the Toronto Subway in a time frame that is half as long as the TTC Subway's, and for much cheaper. Perhaps that's something we could learn from them (which is precisely what we're doing with the Ontario Line, and what Montreal is doing with the REM)?