What do you mean by "calm Lake Street?"...without a complex funding mechanism that relieves that park board of most financial responsibility. They have too few funds, period. There are numerous ways to reorganize the path systems, and possibly calm Lake Street, that could be cheaper.
If you're referring to a way to slow down traffic in that stretch it would be a disaster for the adjoining neighborhoods who would then have to live through more exhaust fumes from idling vehicles and honking horns.
This is a genius idea I believe.
If anything this would allow for better traffic flow because you wouldn't have to allow for crossings at street level in the immediate vicinity.
This means less backed up traffic due to improved signal timings. Less idling cars. Better quality of life.
Anything you can do to improve traffic flow and make the area more pedestrian/bicycle friendly at the same time is a big thumbs up in my book.