I considered a very similar idea a month or two ago and discussed it with Ned and with some of the other witnesses. The idea went cold when none of us could come up with a good way to make it attractive to larger stakeholders. Curation rewards are somewhat superlinear by stake holdings in practice, so a linear increase in SP (virtual) dividends would probably more more attractive to smaller stakeholders (an obvious example being those whose curation rewards are too small to pay out at all). What is worse, the degree to which curation rewards are superlinear is variable as it depends on voting behavior so there isn't a good way (that I could think of) to create a formula that offsets it. Finally actually investing effort in curation has more of a payoff if your curation rewards are larger.

So it seems a naive version of this would just tend to further concentrate voting power at the top, as smaller voters opt for the dividends and larger voters continue to prefer to earn more with curation.