A grant or funding mechanism for part of the upfront costs like other platforms are trying is a quick and easy solution.

Without something more than what we currently have there is little economic incentive to take a chance on an app other than gambling that you will earn beneficiary rewards. Some of which are close to 25%. Which btw defeat the whole purpose of a free decentralised blockchain in my opinion.
If we expect professionals to invest time and energy in the technology of the platform we need to provide them with some sort of incentive. Otherwise we will not attract any development, no mater how big the Steem price gets. We will just see more people gaming the system to extract value.

you could realize a bot and ask the community to set this bot on autovote

This is a really good suggestion and it could be very transparent. People who wish to support projects could delegate Steem Power to it and even vote on which projects to support.

@oracle-d has an interesting business model focused on bringing in outside investment to fund projects. This project and the team are doing a great job it is a great proposition for investments. But it makes me think and I do question why so much money that is already invested in the platform is not being used to promote projects that will help the platform grow and expand. And of course increase the value of their investment!

another great example: DASH. Dash let Masternodes (here it could be steem-witnesses) vote on proposals of the community

This is a great suggestion and I believe a similar idea has been discussed on Steemit but I have not seen any momentum behind the proposals or proposals of alternative solutions that have gained traction.