You sir have a brain :) But one tidbit. Area locks were present in the base game. The spire top on Venus and the house of kings den in the cosmodrome being present and accessible through glitches were areas that were DLC exclusive. I think the house of kings den actually spawned level 20 enemies inside before the dark below was released if you got inside. I'm not an expert, just pointing out a fact I believe in. But a question for you. Vault space being linked to engine management is something that's most probable, but on your point of said vault space straining engine limitations (TBF, 300+ items per person, each with their own coding being loaded instantly can cause some strain). Could said matter of loading vault contents be reduced in destiny 2 by having the vault items load EXCLUSIVELY for the person who access's them? Imagine 5 people with full vaults viewing said vaults in the tower (that's a full lobby). That 1500+ items could cause a strain being loaded for people who can't even see them. Surely there's a way to minimise that amount of required processing memory? Like I said I'm not an expert. I could be waffling rubbish right now without realising it 😂