Maybe tie it to your resort reservation? Off-site guests wouldn't be able to make an ADR then, but that's the price you pay in my opinion. (And we have stayed off-site in the past, I would accept the fact I couldn't make ADR.) Heck, Disney could even sell that as yet another advantage of staying within WDW. But yes, tying it to a park ticket would be a good start.
Disney has a lot of smart people, and my guess is they know this has become a problem. Unfortunately, nothing ever gets fixed as quickly as we would like. One thing they could do immediately is cut down the number of ADRs you have in a day, or multiple ADRs at the same restaurant throughout the stay. I never realized how many people make multiple ADRs every day, then cancel later.
Any way you slice it, it's not acceptable that if you stay in a Deluxe (or even Mod) resort you can't get an ADR at a restaurant you want months in advance, or if you get lucky dinner is at 4:00 or 9:45.