Good idea. I've suggested a similar "investor class" SP, where those who choose to give up voting in exchange for more interest. I like how you have put numbers on it and set a balance in reward pool between voting SP and non-voting SP.

I would like to get rid of the 'flexible' author/curator split though, which has the effect of greatly reducing curator rewards and discouraging real curator effort. We can still have the reverse auction (ideally shorter) but instead of giving the extra rewards to the author, put them back into a pool to pay out more for curation on other posts (in particular the more obscure and less heavily voted/autovoted ones).

Another point in favor: Bot autovoting adds spam to the chain. If even some investors choose to sit passively and earn interest instead of autovoting for profit, it means less transactions on the chain and better scaling.