As others in this thread have said,
for NA TF2, this would not create a new league, but would just be the modification of ESEA (quite possibly leading to better support?).
IMO it's hard to see this as anything other than a win/win for NA TF2.
As for EU/OCE/SA, I'd recommend that ESL reach out to admins and community leaders of the existing leagues there as well and see what kinds of opportunities there might be for working together.
Would love to see big TF2 events on ESL streams at some point :)