I can't imagine this being anything other than prohibitively expensive - you're paying to relocate 20+ players for a fairly long time and putting them in what sounds like a fully professional program, without them likely to bring in any real revenue in return. That's before you get to the part were you'd have to convince the tahs, Brumbies and Force to give up access to the their top under 20s players during the super season.
They absolutely need more rugby though, but I'd look to a formal under 20s comp in the early rounds of super, instead of a 'B' comp. You can then add in a bit more in the way of warm up games before the rugby champs (possibles v probables, shute shield or hospital cup barbarians, hosting Japan, Fiji, etc) and some sort of end of year test schedule after the Super Rugby u19s, ideally a tour.