I assume the new station is intended to be a tribute to the old one as well as a replacement for it. It's a memorial of sorts, but also a continuation rather than an unrelated construct, hence why they gave it the old name, I guess. So I'd assume that they're keeping some of the old design features in honour of the historic Terok Nor/Deep Space Nine
that everyone's familiar with. Let the old station live on in spirit. Plus, for all that the first station was originally the seat of occupation, it was a massively important part of Bajor's history and a unique "landmark" for the Bajoran system. I suppose they'd want to be careful and not be seen as sweeping that history away by making the new DS9 "just another Federation mushroom".
Nowadays, pleasing the Cardassians might be just as important as pleasing the Bajorans. The Cardassian Union is the Federation's ally, and according to Akaar the Federation is taking that alliance very seriously. Maybe they want to incorporate a degree of Cardassian-inspired architecture into the new station rather than be seen as sweeping away the imprint of Cardassian identity?