Several models have had the head lasers usable as rear-firing weaponry, so the turret isn't totally necessary on a production VF-29 for that reason, but the main thing is that aesthetically the YF-29's turret was still a big lump (a streamlined flat lump, but still a lump) on the back of the fighter. In a casual perusal of images online, it seems that displaying the -29 without the turret is more common.
F-35 basis for a Valk: I think SF has beaten reality pretty thoroughly into the ground by now. Maybe a new model will be more streamlined and have the smoothbody low-RCS look now that the F-117/VF-17(1)'s faceted look is out of date, but a mere transforming V/STOL airplane is so...
1982.
Editorial: Besides, the F-35 is kinda boring to look at. Whatever practical flaws the Boeing JSF proposal had, at least the chin-mounted intake and delta configuration had a certain uniqueness.