Boston needs a course and Franklin Park would be amazing. I live just a few houses away from it and know it very well. But I think you are off on believing the city with "go for it."
After a lot of consideration and conversations I don't think that Franklin Park should be the target. There are to many organizations with a stake in conserving that park as it is.
Stony Brook Reservation is an alternative that offers more land, more underutilized land, and is managed by DCR who hosts Nantucket, Borderland, and Riverhead. Stony Brook Reservation was not designed by Olmstead and so there aren't a dozen organizations who want to leave it untouched.
It is still going to take a herculean effort to get a basket in the ground in this city. Probably very similar to what happened in the building of Golden Gate Park's course which took 8 years of sustained effort by a core group of dedicated volunteers.