I assume you mean the authors created more accounts for spam purposes (to hide their activities) and not the curators creating accounts. That has seemed to significantly go away and I would think the likelihood of that is the same if this change is made or not since self voting activities like that always have to operate in the dark.
But from just a straight “should I manual vote vs auto vote” perspective, I think it will overall come down to which gives a better return with minimal effort. Adding value to the manual vote with a layer two solution seems like a steep uphill battle. Reducing auto votes on the base layer seems like the only way and like you said, auto vote programs will just evolve, so detecting it has to be done another way. That is where my thinking was.
Current top authors will lose votes if people change their behavior, but if it is framed as properly rewarding under valued content and improving overall decentralization of the base token, I think the community can get behind that.