Seawall Development will design a new shed-style market next to the old one, on the present parking lot between Paca and Eutaw Streets. The arcade will go away and turn into an open, terraced plaza. But, cool as the first designs look, the building doesn’t seem as important as what happens inside it. Jon Constable, who will lead the project for Seawall, plans a series of open meetings in the old market — the first one is June 26 at 6 p.m. — to hear what Baltimoreans want in the new one. The idea is to strike the balance between tradition and modern trends, between keeping present customers (and vendors) and attracting new ones.