The suggestion that was posted in this particular thread that I was responding to was "[p]erhaps [the existing B SEN lounge] can be turned into a *G lounge, leaving the new lounge for SENs!" The new lounge with 300 seats should have enough room for all so there would be little need to limit that particular lounge to SENs only . . . except to give some an "I'm better than you are" feeling.
In case you haven't noticed it's a running joke in this forum.
But joking aside how do we know a 300-seat lounge will solve the overcrowding problem? Some people have given up going to SEN lounges (in B especially) and going to Business lounges instead. The SEN lounge in A is also overcrowded and some people may come the new B lounge instead.
LH is unusual in providing separate lounges for Business pax and Senators/*G. Why should people who pay to fly on LH C be treated less favourably than *G many of whom don't even fly on LH? And some LH Business lounges are nicer than a few *G lounges I've seen. I don't think there's anything wrong with airlines treating their own status pax more favourably and pax who fly in their premium class for that matter.