The "past" work aspect of your proposal would be your sticking point for passing your proposal on your ongoing future work.Also the hypothetical of "asking for payment before you actually show you are able to do something is not very good practice" is not reprehensible as compared to asking for payment after the fact.
I know it is not a bill; the point of that analogy was to convey an emotion that your proposal can induce. If you understand that then you'll be able to better maneuver this situation.
Your last statement is not the best PR on this, if you care about such things.
I would prefer to feel in a strong position to support you in this. Hence bringing the points up that makes it feel hard for me to do so.
There is a win/win/win here were you get funding and the community is happy about it instead of tore over it, but itll be up to you to get it there or not in the end. I feel that if you stick hard to this proposal as is, then it will cost you more in the long run in terms of the community that would support your proposal under the proper terms, but not as is now.