Witnesses are at best basically business minded folks (being nice here) and less about long stability, growth, and sound ideologically minded thinking economist.

If the thousands of the multitudes of BTC core miners can unite to refuse to give up their fat transaction fees and slow down the progress of Bitcoin adoption as a transfer of value, do you think a simple band of 20-30 top witness would ever be able to openly debate and agree to collectively give up a single dollar of sacrifice to improve our already quasi-centralized/decentralized social consensus network?

Since asking Witnesses to sacrifice Steem for price growth is near impossible, aka reducing their share in the 10%.

Keep it at 10%, hell, we can even increase it to 15%, how about 20%....BUT 

Lets ALSO increase the number of witnesses getting bigger rewards. The competition will eventually breed improvement. Slowly at first, but inevitable, it will accelerate, imagine 1000 Steem miners, can you imagine how many innovations we'll have on Steem if we attracted so many technical investors?

We should just make Steem an ever-improving decentralized network....raise the top 20 witness number gradually, say 1-5 new witness sharing in the top 20 pool over time, say every 3-12 months.

Just a Simple Example: As long as there is 50-100 active witness in the network (check by math so there is no need to debate this amongst witnesses), we increase top paid witness number by 1 every 6 month (for every 50-100 witness, so if there is 400 witnesses, we should see at least 4 or more new top witnesses). At today snail pace of sustainble witnesses, we should currently see a minimal 2 new top witnesses, and in 10 years time (assuming we find a way to reward curators and content producer on Steem so it doesn't degrade till near abandonment), we'll see at least 40 top witness sharing the lion share of the top pool in 10 years time....possibly 200 new top witness (and by then, we'll probably see Steem at $100 :D )

So in theory, if this proposal attracts more people to become witnesses aka more miners to secure our network, and to compete with better reliability, full node servers, and new daap/community/innovation proposals and implementation.
 
No DPOS/DAO/token/smart-contract crypto has this today, it will give Steem a leg up, and better crypto and institutional investor creds, aka funds flowing in if we did this, making up for the decentralization cost of increasing the pool of witnesses and rewarding them.

ALTERNATIVELY:

Let Top 20 Witness share of the witness pool decrease over time, eg. currently it what 20/21 share almost all the 10%. So instead of keeping 95% of Steem witness income going to only 20 witnesses FOREVER!, let it drop by 5% every year until it reaches 20% (say after 12-14 years), giving more rewards to witnesses from 21 to 100 or beyond.

Incremental improvement to decentralization will help the cause of Steem. Not just stability, but greatly so with the financial community and crypto community. I say if this works, you'll see EOS, Tron, etc start doing the same, improving all 3rd gen crypto over time.

ONE OTHER THING:

 And goodness sake, please implement vote expiry....that's just a non-brainer. Every vote should only last max 6 months max, of FFS lets be innovative if whale, orcas, and dolphins keep renewing the votes for the same witnesses (respectful fcukers or shifty mofo) the vote weight should reduce by 50%, so new upcoming witnesses with new votes gets a chance to rise up (do stuff to make Steem proud and not just make money) and get gradually increasing rewards so they don't end up proving themselve for next to nothing. 

COME ON EVERYONE...WHY NOT?