Update the Proposal structure so that Proponents may bond funds into a contract, which will be used for funding the proposal if it is accepted, but will be refunded if it is rejected.
This kind of proposal could also cost a little more, as in, be a higher tier proposal.
This would allow community members to donate to proposals. They could also have requirements, such as, the DAO/Treasury or Anonymous Individuals must also contribute a certain amount - all of which would be refunded to the contributors if the proposal fails and for which the proposal cannot pass unless the requested contribution is achieved.
The proposal could also have a time limit on it, governed by the proponent, such that they (and all contributors) will be refunded on the deadline if the proposal has not passed.
Maybe they could be allowed to deposit BEAM, BEAMX, and NPH for the funding of the proposal. There should be some kind of update mechanism which portrays the total value of the proposal in one of the currencies, such as BEAM or NPH (US$) so that people could easily monitor its value at any particular time.
Maybe the proponent could also contribute more to the contract at any time prior to completion of voting. Obviously it would need to be transparent about the current status of contributions by all parties involved which covers 3 categories, Proponernt Treasury, and Anonymous Contributors (anyone else).