"The only people who I can imagine objecting are photographers, who, during particularly busy periods, will no longer be able to get shots of the hill without people in."

As with all art, living things always add something to pictures. And it's good to have people in shots of Silbury so as to convey the sheer amazing scale of it.

I also think this feels right. The strengthened paths at the Rollrights with grass growing through them are zero aesthetic problem. And of course, such a path wouldn't be interfering with archaeology, whereas strengthening the path on the hill would. But best of all is the fact the public would protect the hill by becoming Shame Wardens. ;)