The problem with Wildernest is that they went tits-up, what, 20 years ago? So if your vehicle is newer than 1999 or so a 'Nest likely won't fit (not well, at least.)
To say nothing of the fact that fiberglass cracks and breaks down over time. Yes, I know you can fix it but it seems to me if you're using a 20+ year old fiberglass topper, you're on borrowed time.
Wildernest was one of those companies that was ahead of its time. I'm a little surprised someone hasn't tried to resurrect it now that RTT's are all the rage.
Of course, it's likely that the problem now would be the same as when Wildernests were still being made: The dilemma of "cost to build a quality product" vs. "what consumers expect to pay."
With standard fiberglass caps currently going for upwards of $2k or more, a Wildernest would likely be at least double that if not more. And for $5k you still don't have a real "camper" just a nice RTT with room to stand up and change clothes.
IIRC that was the problem with Wildernest when they did make them. People loved them, but they didn't love them enough to shell out the bucks for them.