I think one thing people are going to get confused in what you're asking is the difference between making map variants a-la forge world and using Grognok to create areas in their entirety. I'm very doubtful we will get the tools to create areas using Grognok; it doesn't fit their goal of everything existing in one world if we can arbitrarily build levels. However I think PvP arenas with forge capability make perfect sense. You can combine custom games with forgeable levels into some sort of "training grounds." In the training grounds guardians would take advantage of a modular environment to prepare themselves for the challenges of the wild. This would fit better with the atmosphere Bungie is trying to create IMO.
However I wouldn't expect this at launch. I envision things like player economy and forge world to be mechanics to sweeten the pot of DLC content. The less moving pieces at launch the easy it will be to pull off a successful launch with the side benefit of having good mechanics to trickle into the game over time. Forge world would definitely be a reason for people to start playing Destiny again between major content releases.
English
-
Interesting thought: What if forge objects were unlockable/collected through gameplay? It might limit the forge community if done wrong, but it would also be really cool if you found schematics for a super rare piece out in the wild. Then you could have a signature piece in your maps or help your friends out by spawning in said piece on their map if they needed it. That could add a lot to the community as a whole if done right.
-
Or at the very least you wouldn't unlock certain arenas and their respective items until your character is that point in the game. Can't have a Venus arena to forge if you haven't been to Venus. However unlockable forge items would be awesome for Easter eggs; I.e something like finding the schematics for a very familiar roundish bunker in a canyon on Mars.