I believe that the Mark I Advanced Power Armor has no place in Washington DC. I have two reasons for thinking this.
My first reason is that I feel having an armor identical in appearance to the Remnants Armor makes that armor less unique. Not to mention the fact that in Fo2 the two versions of APA were not identical in appearance. I feel that the way that it is currently implemented feel cheap/shallow and very out of sync with the rest of TTW.
Secondly, and more importantly, there are serious lore issues with having this armor appear in washington. To begin, we must remember that MKI APA is superior to T-51b. This is not reflected by the armors statistics in TTW. Another issue is the fact that if they had had this armor, the east coast Enclave would never have had to develop the new "Black Devil" power armor, which is actually weaker than T-51b and earlier APA models. Basically, it defeats the entire purpose for the existence of the "Enclave Power Armor" from fallout 3.
Another issue is that, in vanilla FNV, we do not know whether the Remnants actually have MKI or MKII east coast armor. If we include the MKI armor in TTW, we are de-fact declaring the remnants armor to be MKII, which does not necessarily reflect FNV lore.
Basically, what I am trying to say is that having the MKI armor in Washington creates multiple lore problems for both DC and FNV, and thus is beyond the scope of TTW. Besides that, there is not a good balance or gameplay reason for it to be there in the first place, and it actually detracts from the DC experience. If feel that it should be removed from levelled lists, so that the East Coast Enclave only uses the original Fo3 armors.
