Good to see you popping in! Hiya!
Why would T4 even take precedence within this project? Separately, sure, especially driven by new enthusiasm, excitement, passion, and inspiration from that other new experience, but a thousand FMs weren't made with T4 in mind, and some of them, and fanfiction, were made using what we've all contributed here. Every few months I get a person asking me for a copy of the herewego map. I don't know who else has been asked or who found it on their own, but I can't be the only one. If this one could just be finalized, and the new one can be built cannibalizing what T4 doesn't account for, if it's even compatible, it'd just ease things and get things done. Look how long it took to shoehorn the old games into and around T3's City. If this map won't be finalized, I'd kinda like it to be officially abandoned. If someone comes out of the woodwork and decides to do it after the fact, great!
We know that EM has the TDS design docs, and one ex-LGS on the writing team, but no word on old Thief materials. We never saw that original map, unless the Talisman Map was the original afterall, which they quickly and thoroughly outgrew and didn't hold to.