Lockheed (Martin) are a brilliant company and if anyone can pull off the JSF, it's them.
But, to me they got the basic concept wrong right at the start. OK, with the utterly brilliant resources at their disposal, they might be able to work their way out of it- a bit like Porsche did with the 911- but there's no getting away from the decisions made right at the start of the program.
There were some great minds involved in the Harrier, and at that time a great deal of effort was expended by the worlds leading aviation brains in other countries, trying to solve the problem of a VTOL fighter.
HS pulled it off with the P1127/ Kestrel/ Harrier/ AV-8C series. Everyone else got either nothing or a clunker.
I think the coupled lift fan thing is a dud- for the same reason that the other VTOL aircraft apart from Harrier were duds. Dead weight- and let no-one say that JSF doesn't have weight problems!
If they simply had to have a new jet, they should have maybe started by redesigning the Pegasus, and worked away from there.
You can't polish a turd- even if you're as good as L-M.