A couple of points.
First, UCF isn't in the BEast and is highly rated by Steele. I don't know how this turns out to be a solid point for joining the BEast.
Second, the BEast is unstable and a national laughingstock right now. Not a great time to join.
As to your points:
1. BYU will have major financial disincentives to keep them from leaving the BEast. Probably 20-30 million dollars worth. They can stop Indy at any time, but they can't easily shell out that kind of dough.
2.There is little chance that BYU will get the same TV deal they are getting now.
3.That same argument can be made for BYU with a better schedule as an Indy while not being affiliated with a deteriorating conference.
4.This is a personal preference issue. I personally think it is vastly overblown.
5.As an Indy they will also be 'stretching the recruiting base' and the presence on ESPN has increased interest considerably.
Not sure why you think BYU had two really bad years to start Indy since they've only been independent for a year.
I'm a huge BYU fan no matter what, but I will be very, very disappointed if they join the BEast or re-join the MWC.