I reckon that there are a couple kinds of potential funding that may be beneficial to stakeholders. Some endeavors are essential and unavoidable to the entire community, and these might be budgeted from the inflation mechanism you propose. There are also less critical matters than infrastructural development, and amongst these items may be affiliate marketing programs, marketing itself, and etc.
I suspect that a mix of funding solutions will prove ideal, with some things being comparable to roads and defense in a national budget, and others comparable to welfare or education - less fundamental to governance - and more appropriately funded via donations, or mechanisms less unavoidable than simply taking a cut of all inflation.
I would like to see more proposals over time, and expect the community and particularly the @steemalliance working group to put more forth as folks give more thought to these issues, and am confident ongoing discussions and polls will be requisite to successfully determining our eventual course(s) of action.
Initially, I believe we can expect donations from @steemit (and possibly other stakeholders) that will be adequate to get the ball rolling. At this time I don't think we have adequately considered these issues, or have nominal data to examine regarding proposals, to effect long term solutions.
I look greatly forward to your own considerations along these lines, and believe the cut from overall inflation will be necessary to effect core infrastructural development in exactly the way you propose. However, the community has demonstrated various voluntary mechanisms of funding developments, and while such purely organic, voluntary devices certainly should continue, we would probably benefit highly from hybrid mechanisms that more formally potentiate folks regularly contributing to systemic developments of less critical infrastructure.
I also agree that witness funding should remain separate from either type of funding mechanism, in order that any problems with funding the security of the blockchain aren't obscured or complicated by the novel mechanisms we are here considering.
Thanks!