Got to see a 14D @ Reno years ago do a routine, and while no fan of GE, that thing had moves no Pratt Powered 14 did, it was breath-taking.
Yet everything I read about the F18 series is it has a drag penalty of something like 20%
I don't know, put stealth aside for a moment, something like a double delta folding wing design with off the shelf components ( think F-16XL-ish ) could be cobbled together and may work better than what they have now. And give up on this VTOL fantasy, it isn't worth the hassle. STOL / unimproved fields capabilities yes....
STOVL is no fantasy.