I think this would really improve the Halo experience. Destructible terrain adds more realistic value and just plain fun and uniqueness to any game, and this would fit in great with Halo. But if one wants the original Halo experience, then he can place indestructible terrain.
Think of it this way. Let’s just say you’re in Forge, and you spawn an object. You can access the object’s menu and toggle an option that decides whether the object is indestructible, like the objects in the other Halo games, or destructible. Could you imagine shooting a shell out of a Scorpion at a building, and then watching the building crumble and fall on and around the players that were taking cover in it?
Once again, in my opinion, I think this will add a new element of uniqueness and fun that the Halo series should try to expand upon.