Perhaps it would make more sense for the NBA’s free-agency period to come before the draft.
When you go after a free agent to fill a need for your team you know that player is a solid bet because you’ve seen him compete in the league for a number of years, as opposed to draft candidates who are still unproven at the NBA level.
If the signing period for free agents came prior to the draft, you could pursue the pros you know will help your team and then fill out the rest of your roster at draft time accordingly.
For example, if the Nets had already signed Deron Williams, would they have made a draft-night trade with Portland for Tyshawn Taylor? Brooklyn may still have selected the promising young PG to groom him for a bigger role down the road, but they might have played their cards differently if they had locked in their All-Star point guard before the draft.