That's easy. The South End, and all of Boston, would benefit enormously if the NEIDL were retrofitted with all of the authentic fixtures, bargains, discount policies, and salespeople from the original Filene's Basement. That pale imitation in Back Bay isn't fooling anybody. I would personally crawl on my hands and knees to the South End if I had any hope of snagging another pair of bronze Ferragamo T-straps for $13.12 (all of it donated to charity).
On the ground level of the former Biolab, if there is one (I haven't crawled over there to check it out yet, for some reason), I think a Chacarero, a mom-and-pop bakery, and an Anna's Taqueria would make everyone happy. And if there's still space left over, how about a dance club and a multigenerational community center?