I'll be the first to admit the frontpage looked less trashy and the post quality increased significantly, however interaction and growth were the consequences as legacy and stronger SP users were the only ones who could contribute.
I support the idea of bandwidth delegation pools, it will be a while till they are implemented though so in the intermin the 10X helps however is not the long term solution to this problem.
Your argument does have merits and is worth further exploration if the economics behind it will scale as long as you presume they will.
If new users are able to do sufficient interaction on the freemium model to motivate them to earn or purchase steem it could work.
That said we also need to presume they will not in the near future go to an exchange to buy more steem and will not insert cash into here directly as they cannot through blocktrades.
Therefore there needs to be enough incentive for them to learn to do so, if they hit their limits.
We will see how it goes for now.