Donald Sterling willingly spending ~$60 mil per season and the NBA is demanding a hard cap of $45 mil? Wow. You have to think that $45 mil is just there to draw the union's fire, so they can flank them and get bigger concessions in contract guarantees before making a showy retreat in the final cap figure.
I'm definitely a believer in the hard cap, though not at $45 mil. The luxury tax just exacerbated the inequalities of a soft cap by incentivizing cheapness for the small markets and making the big spender club even more exclusive. Abolishing the luxury tax altogether and using the tax threshold as a hard cap makes a lot of sense.
"Super" bird rights and max contracts make little sense in a hard cap though. If the hard cap is firm, there's no need for further limits, unless the union feels it necessary to subsidize the Udonis Haslems of the world at the expense of the LeBron James'.
Creating a max just to allow the home team to field a better offer to its free agent is overkill. It would be much easier to allow eash team a small bonus pool of cap-exempt cash (limited to say $5 mil) that the home team could use on their own free agents as a unique signing incentive. The bonus would not be incorporated into the salary and thus would not factor in trades or break the hard cap.