Supercharging your vote

Not sure what you mean by this. I understand the concept of giving more power to a vote temporarily, but I don't see how you can implement it. If you meant to say that I could add SBD to my vote that would be transferred to the payout directly, that doesn't work. The optimal move then would be to always supercharge and upvote yourself, since you'd be getting almost all of it back. Whales would start doing it and it would make the visibility issue much worse.
If you meant something else, please let me know.

For #2, I'm pretty sure it can't be a fixed rate. You'd have to effectively pay based on your remaining voting power %. I'd have to think a bit more about this, but intuitively, I'd say that the cost of bringing your vote back to full power would probably need to be higher than anyone would be willing to pay for it.

If you were to empty your votes in a day with ~40 votes, then you'd think the cost of bringing your voting power it back up to 100% would be 40*avg_upvote_worth - but I could be wrong.