One thing that I like in Bitshares governance model is the committee. It's elected set of users who have power to change blockchain parameters. Although I have to admit it's working very poorly in practice currently because nobody seems to get how important it is.
In theory, a governmental body like the committee should be a group that focuses on the business side of blockchain governance. They need to have business skills, with a little bit understanding of economics and psychology. Blockproducers are the tech guys, they should focus on technical side of the blockchain. In Steem these roles are combined.
We are now seeing a good example why it's not a good idea to combine the roles of tech workers and business decision making. Steem price has been going up so much that new accounts don't have enough Steem Power to have great user experience. The Steem blockchain limits how many transactions users can make based on how much SP they have, and currently new users aren't given enough when the account is created.
@timcliff has taken the initiative and brought up the issue. That's of course great, but it also shows how the system isn't perfect. This is a reaction to a problem instead of proactive problem solving to prevent this kind of situation.
Ideally a blockchain should have a role for somebody to think things like this in advance. It could be just a one person or a group. They should be aware of the current state of blockchain, have good understanding how things are evolving, and clear vision what the ecosystem will be in the future. Then they can either change the parameters themselves (if it's a feature built-in to the blockchain) or give recommendations (if it's the blockproducers who have the final say).
This might become a problem in EOS. It will have Steem-like system where blockproducers have the power to make changes. The role of a blockproducer will be demanding: not only they need to be highly skilled in running a complicated server reliably 24/7, but also have a good understanding of economics and some business skills. And not forgetting the constitution, which basically requires blockproducers to understand law, too. They will have huge responsibility. That's why my recommendation is to separate the roles of blockproducers and the rest of the governance. Let tech guys take care of running servers and free them from politics.
For Steem my short-term recommendation is to unofficially elect somebody or a group of people who will focus on blockchain economics, including things like blocksize, rate-limits, etc. They should give recommendations to witnesses in advance to prevent problems like new users not having enough SP to use their accounts properly.