I think burning some Hive has long been regarded as a way to "positively support" the community and the token.
There are a few initiatives dedicated to burning Hive/HBD, most notably the @buildawhale account creates daily "Burn Posts" that take about about $500-$700 worth our of circulation every day (check the comments on each post). The @centtoken project runs a similar initiative, although on a much smaller scale, but it all adds up. Same with @voice.direct.
As you probably discovered, there are a number of posters who regularly burn part of their rewards.
Anyway, I like your suggestions because they are more broadly community based. People like contests, so that might be a good way to try. I'm not sure witnesses would be into burning 50% of their rewards because they need to pay for their tech somehow, but those in favor of ramping up Hive's burn rate might be good to approach as "sponsors" of contest prizes.
I think the idea would work best if the outcome is a "net burn" situation... a "topic of the week" perhaps; all participants MUST make the @null account at least a 25% beneficiary; prizes for 1st, 2nd, 3rd... maybe even turn it into an annual "league" where people can accumulate "points" towards an end-of-year grand prize of some sort... 1 point for entering, 5 points for 3rd place, 10 points for 2nd, 20 points for 1st to encourage people to participate regularly.
Yeah, I could see that. Certainly worth exploring!
RE: My Gleanings on Hive Inflation & A Thought on Burning HIVE