A promise is a promise, if you make one incorrectly you suck it up and deal with the consequences. If I had promised to give $10k a year, but my financial situation changed and I had to reduce it, should I expect my seat location to remain the same because the financial situation is now different?

Why not take the 1000, 2000, 5000 (whatever number) best seats in Lane and make a separate waiting list for those - totally based on current giving - the more you give the higher up you move on this list. As people don't renew, pass on, etc. the high rollers get good seats and have a longer term buy in - both in money and time - don't just peddle the seat license program of the day that appears to be subject to change anyway. Potential givers would complain that they don't have a guarantee when they'll get seats - could just tell them it'll be 3 years, we promise...

Don't demand more from loyal givers to maintain existing seats if that's what they were promised, but you can tell people with seats just outside the specified "good" seats that to improve you have to step up. People looking to contribute now are not blind to how long time contributors are treated - they'll be there one day.