The city should put at a map of ALL the land it owns (and isn't using) in the entire DT area and invite proposals for ANY and ALL parcels.
No minimum price, bidder just includes that in the proposal. See what comes back. At least that would tell them what parcels the market desires most, evne if you declined them all. If you get multiple offers for the same parcel(s), then rank them based on price, 20 year tax return based on the project, and snergy potential with what is already in that location.