So what your saying is that for people who didn't buy the DLC, if they try to join another players lobby and got kicked out because they didn't have the maps, would be so ridiculously crazy that 343 and Bungie will never, ever do it?
Actually, Bungie already did. 6 times. Every DLC pack has been forgeable since Halo 3, and whether you can make more or less objects doesn't matter, so please make SURE you know what you are talking about before you post a reply shooting down someones idea to try to come off smart.
On topic, Although I would like this, it is not going to happen for other reasons than the genious I quoted mentioned.
Marketing. 343i along with every other company try to make their DLC packs appeal to a large audience, and boost their game. Since not everybody forges on Halo, the map pack already appeals to a smaller scope of customers. Not only this, but if the maps were simple blank canvases to forge on, and provided no IMMEDIATE matchmaking boost, then game reviewers would slap horrible ratings on the map pack, and the sales would once again drop to an even smaller protion of the gamerworld, being the 'Halo fanboys who like forge who will buy a game no matter how bad it is just because its Halo.' (Yes, I understand people would make maps on them, but they still need default disk maps such as Paradiso, Hemorrage... ETC.)
Does that explain anything to you?
What would be a good idea for 343i is to make a map pack include 2 matchmaking maps and one heavy forgable map. On the forgable map have one default map already made and have a canvas ready to be downloaded if need be. It would be like what they did with the last map pack. They had 2 matchmaking maps and 1 firefight. Some people don't like firefight so the created a smaller scope, but the other 2 maps broaden the scope back out to the rest of the population. So this could work if it was done correctly.