I would echo the focus on the route from Sunshine, its an absolute must do. But I would hike into Mt. Assiniboine from sunshine rather than out which makes that leg of the trip mostly downhill. Just make sure to pack lots of water for the valley of the rocks, I believe its about 12 km with no water source.
My favorite route is in from Sunshine then out via Wonder Pass (way prettier than Assiniboine pass). Downhill the whole trip! The only part that is a real slog is the 7 km through the Mt Shark rec area where you see a sign every 500 m that tells you which way the parking lot is but don't tell you how far. It is a lot of km per day but its quite easy hiking and you can have your gear flown in if you want (save the flying for when our knees don't work so good anymore :P).
Also, if you like some seclusion with your hiking I would consider camping at Lake Og, especially if you go over a long weekend. Super gorgeous campsite that is just a few flat km from the Assinaboine area. You can do all the same day hiking from there in the Assiniboine region without having to be in the gong show that can be Mt. Assiniboine Campground.
Not the fastest, but I get to where I am going and enjoy it.