has already bee in the loop...
Once apon a time that could perhaps maybe happen, but most likely not in our lifetime :p
And honestly, If you want to build a vst, then you already have several 'kit' options...
In my opignion, lmms devellopment should focus more on making lmms compatable with vst' versions, rather than integrating a vst builder in the software.
and finally -There is a gasilillion and one vst's already.. Who need to build any :p