If it were me, I'd keep the three tiers and just sweeten the elite rewards at 75K.
Perhaps AA should introduce regional SWUs at 75K, issue like 8 at 75K and 8 more at 100K and give EXP the option to upgrade intl itineraries with two of them.
AA should most definitely keep the e500s, those e500s make a lot of money and because people pay for them, it pays for the above average domestic F service that AA has.