Something else that would be interesting to develop is a kickstarter style funding system. The difference with a normal post is that the poster would define a target payout and a limit date among predetermined maturities, and would only receive the payout if she accrues enough votes to hit the target before maturity. At the moment, to keep it compatible with the current system, the accrued funding could be calculated as the sum of 1-day payout (so minimum maturity would be 1-day) and the subsequent 30-day payout (so maximum maturity would be 30+1). For this particular case, payout would have to be paid entirely in SBD.
With that kind of system, Steem could easily become a crowdfunding plateform since, as a matter of fact, the post reward system is effectively already being used to fund projects.
Where this connects with the bounty system is that this allows for another way of funding new developments where instead of setting a fixed price for completion of a given task, the inceptor of the idea could instead publish it as a call for tender, and let interested developers could make an offer with specs, and cost, and let the community decide which it likes better. The system can also be integrated with the new escrow system of release 0.14.0 so that the funds raised will only be paid upon completion and delivery of the project.