As long as it depends on the trust of customers, why not make the method of financing through donations? There are some successful projects that rely on donations.
I also believe that the costs of running escrow service will be cheap if you gain sufficient trust.
Overall, how will you gain trust? There is no such thing as decentralization and you are suggesting to the parties forms based on trust, such as a multi-signature address.
You can ask some famous people in the forum to manage this service while getting trust, it's the cheapest idea.