I really like the burning of tokens idea, we clearly have to find more ways of pulling STEEM out of circulation other than just powering it up, its clearly not a motivation for people to have strong hands or see any benefit.
I think the instant trade for a 5% burn fee seems fair and it will also discourage users or rather allow them to think twice about powering down to sell if they have a smaller stake while whales can do their thing
I would like to see more ways to burn STEEM. I like what LEO is doing with burning bid bot bids and promotion tokens are burned, I think those are viable options too.
I'd also like to see with SMT's and SCOT tokens creation of Smart contracts for services that also burn a small amount of the tokens