Well, Chris, here's why I don't think many people would jump on board with this.
Let's say your media pack is finished, and you want to start selling it; you price it at $10. First you have to take off a percent for your payment method (Paypal for instance), then you have to account for taxes. Let's say you are now down to $6.50, which is yours to keep.
You decide to put your pack in a "Starter Media Pack", the pack sells for $20-30. Many people who frequent these forums either wouldn't buy it because they can't afford it, or they only want a portion of what's in the pack (which means they can still buy your pack seperately...assuming you haven't signed an exclusive agreement). Those that have made their packs available in this Starter Pack will recieve a much smaller percentage than they would have if they sold it seperately.
You would be limited as to how your product was displayed/advertised, and pricing control would be limited as well. The only solution I can think of is for TGC to "Buy out" some of these media packs exclusively from the artist; of course this could get a bit pricey for them depending on how well the pack may or may not sell. If they did this then there would be certain criteria that would have to be met (a good example is the requirements that TurboSquid has in order to get their "Game-ready" stamp) to ensure little to no work on their part in packaging everything up (such as poly limits per object, file formats, UV Mapping, etc.).
I'm not saying your idea is without merit; I am coming out with a pack in the next few weeks for sale, but I will maintain control of it for now. It's not a bad idea, but it would have to be done right.
-Keith
"Some people are only alive because it's illegal to kill them".