What else are you going to put there???
Lets start by saying that I think the City has much more important things to attend to than a YDS redux. Some minor tweaks could be made, for now, to make it just a tad less.......well, the way it is......... But a true fix, which has to include the surrounding buildings, would be an enormous and expensive effort.
But to throw out my fantasy, let's start on the north side of Dundas. Tear the entire Yonge-Victoria-Dundas-Gould block down, there's nothing redeeming there.
Rebuild the original O'Keefe Brewery in the north-east quadrant of the block, as a working micro-brewery, with modern environmental standards, and a design that's suited to tours and such, but otherwise as close to the original as practical.
Rebuild the Empress hotel at Yonge-Gould as a working boutique hotel
Rebuild the Biltmore Cinema with original marquee to its south, but create a new, compatible south elevation that would give it additional screens and an animated retail frontage on both Yonge and Dundas; then set the building just a bit further back from Dundas allowing for an iconic streetcar stop canopy and a row of high quality street trees.
To the south, kick Shopper's out of that nice heritage building and create a restaurant worthy of that space whose patio can spill out onto YDS.
To the east, remove that ghastly City-TV / Torch building, not sure on any replacement structure there.
To to the west, restore the original Dundas Arcade entrance to the Toronto Eaton Centre. All of it, including the hanging gardens.
Now we can get to YDS.
Remove the Green P underneath, revenue-loss be damned.
Remove the canopy on the Dundas frontage which just cuts it off from the street.
Replace the canopy with a single row of trees in super high quality, high soil volume planters with irrigation.
Go with the same planting concept on the south side.
Plant Sugar Maple (with good enough soil conditions and moisture and minimal salt, they should be able to work and be healthy, and there's your iconic Canadiana for the tourists, two rows of Sugar Maple frame the square and give off the vibrant red colour in the fall.
Uplight the trees at night.
On the north side of Dundas and on Victoria, plant Aspen giving off a vibrant yellow framing the red.
Leave the centre of the square open except for a better proportioned, scaled and graded stage that doesn't feel so ugly or obtrusive but still allows large performances.
Incorporate a snow-melt system, so the square is entirely free of salt, snow and slush in the winter.
Lose the current water feature. It's not a value-add. Incorporate 5-seasons of annuals into a few select planters (less is more, don't clutter, but make sure the square feels inviting year round.). Bright Red Tulips in Spring, Warm native Sunflowers and Bergamot it the summer; (purple and yellow); Mums in the early fall, flowering Kale in the winter, mixed with Red Osier Dogwood twigs.
Allow any restaurant facing the square, with a special license to serve people at tables in the square.
There, and all for under 2 Billion. You're welcome.