Because there are a couple of different 'forest-like' concepts here, I am going to put a thought for this and other parks.
I'd really like to see more native plants brought in, even to table-top or manicured designs.
Many species are every bit as durable and require less help than many non-natives to survive. Yet, many have gone missing over the years from the Toronto landscape due to
development/indifference, invasive species and the failure to use native plants more often in landscape choices.
Most native tree species are well represented in Toronto, a notable exception being butternut.
There is one species we could add more of (but not too much, as I remind folks in threads here often, you don't want all one thing, if disease/pests hit, its bad news)
https://en.wikipedia.org/wiki/Juglans_cinerea
But there's a lot more we could do w/flowers
My favourite of the day to champion, Wood Lily.
Its extremely common in cottage country. Beautiful, bright, cheerful, once established it can dominate a space like no one's business; its a great forest edge species. Yet we only see the non-natives used, even w/lilies.
https://en.wikipedia.org/wiki/Lilium_philadelphicum
Another wonderful choice would be Cardinal Flower. Now these like marshy, wet sites, though they tend to grow on the drier parts that only a flood a bit during spring or after a heavy rain.
But any park with a pseudo-natural water feature could include these thoughtfully, a great plant for swale-type areas too.
https://en.wikipedia.org/wiki/Lobelia_cardinalis
So many other great choices could be made.