You guys wanting to get rid of the draft may as well fold the Midwest and super small market teams while you're there. You'll basically have a European soccer league where the same teams are successful every year.
You say this like its a bad thing. How is the current system working out for the small-market teams? I would say that a team like the Spurs would still be successful based on their ability to find the right players for their system and coach them well.
The NBA would love for there to be 5-6 super teams that will draw ratings every game they are on. Parity is really bad for leagues overall - even the NFL which touts parity as a good thing likes that it has teams like the Patriots, Cowboys, Steelers, etc. who are loved/hated no matter the record.
Fans like dynasties.
But even so, with a fixed roster of 13 spaces (?), five starters, and a salary cap - teams like Milwaukee will still be able to attract good players, and if they do a good job scouting and coaching, they could be a contender. If they are a contender, they can attract better players to turn them into championship potential teams.