What I'm picking up on looking at the announced matches for Hammerstein so far is that GCW is heavily favoring their "outsider" talents for this show over their core group, and while that's understandable it also feels like the opposite of what GCW is about right?
Not really. GCW and honestly several other indie promotions push "outsider" talent for one of two reasons. The first being getting more people to the product and exposing their fanbase to other wrestlers and hopefully they will want to do more GCW shows and vice versa, meaning the fans would want that person back and all. The second is because of storylines that play out either in the long term or short term, an example is 440H! v H2O, 44OH! declared war on H2O and ran amuck on the promotion until Matt Tremont drew the line the sand and had a final showdown, and it was great. In the end, the home talent may lose, but soon they get their wins back/get a redemption per say.