Many thanks for the multi-updates - bookmarked for further investigation.
One thing though, the slider is already available to everyone at chainBB forums . Even if a user does not post there, every article published on Steemit appears on chainBB, therefore everyone can vote on any article using the slider available on chainBB.
I see no logical reason why it is still considered a "bonus feature" on Steemit when it is already freely available.
The dev team for Steemit has decided that this is a "power user" feature, and so is not opening it up for users with less than 500 MV of SP.