I have another solution. Reduce the curation for big accounts (we need a good definition what big is, maybe > 50000SP) to 1/2 and double everyone elses curation rewards. I don't know the math for that, but it should be possible to use some multiplier when the pay out time comes (the blockchain doubles it because it takes into account your SP).

Or: define different stages for curation rewards and distribute the "cuts" from big accounts to the curation of small acounts. Like 0-50000 SP full curation + full distribution share, 50001- 100000 SP cut off 1/3 and put it in a distribution pool. 150000SP cut off 1/2 and put it in the distribution pool. 150000 - 200000SP cut off 2/3. > 200000SP cut off 70%. (this is just a numbers example to make a point)

It's a big enough raise that it will change the distribution dramatically, but not so big that investors don't get a fair share in my opinion. This process would take a lot of time to show some effect (maybe a year or 2) but I think it would work.

And remember it's just curation, they still get their over paid post payouts or lending payouts.