My opinion (non-expert, running a stock LGT) is that owners say there is a need for a "bolt-up" turbo because they want to run more than 300whp on the LGT without going FMIC or doing other upgrades.
But what we are seeing is that there are a few turbos that can pretty much hit that mark (VF52 for one) on pump gas, or get very close.
But honestly, at that point the owner really needs fuel upgrades and to replace the stock intercooler anyway (since it'll blow it's end-tanks open).
So unless you've got a concept for, say, a bolt-up turbo that provides lower boost lag, faster transient response, lower boost threshold, and the same top-end as the VF52 while providing a more reliable design....
Well, I don't think you'd sell alot of them otherwise.
Personally, I'd like to see a few more ball bearing and/or twin-scroll style turbos for the LGT that offer superb low-down power (i.e. 2000 rpms) while still maintaining a good top-end (say 260-280 awhp). Right now, those turbos are damn hard to find.
Just my .02
P.s. I could be wrong, but I think a twin-scroll style turbo with great low-end power and a top-end of 280whp would be good for a ~13.2-13.5 second 1/4 mile time. I think alot of owners would be very happy with that result combined with the daily drivability.