1) BTC max 15-of-15. Pros: - BTC is the world's number one. Cons: - Group of 3-5 smart cheaters can play 15 honest people. - In order to participate in multisig you need to publish your public key. Due to BTC design, public key becomes really public only after first sending transaction. Or you can explicitly publish it in plain text. Right now it is safe, but in the next 10 years it will be unsafe because quantum computers will be able to restore private key from public key. Untouched BTC addresses will remain safe, but public keys - no. (however, developers have enough time to invent protection)
2) NEM max 64-of-64. Pros: - It is practically impossible to write so many fake lists, someone will certainly identify cheating. - Built-in messaging support, and public and private. Cons: - NEM is little-known and is slowly getting down - https://coinmarketcap.com/ - number 72
Multi-signature address is like a safe box with several locks. Key holders can open it only together. For example "5-of-7 multisig bitcoin address" means that there are 7 keys, and any 5 of them are needed for sending bitcoins.
BTC allows only up to 15-of-15, but other cryptocurrencies allows much more keys (for example https://nem.io has unlimited M-of-N)
The idea is simple - groups of people with similar targets can top up multisig addresses in order to prove their intention to pay.
Your list may be very smart and honest but it is just a declaration. But sending real money to separate address looks much stronger. Potential agents will see not just words, but real money already prepared for them.
And by the way, it can rise motivation for donors significantly. There are a lot of cheaters here, but cheating with multisig address is practically impossible (or at least is much harder).
1000 perfect lists with 100 BTC total amount = 1 "unit of trust"...
I found two possible alternatives: https://member.cash is BCH-based, but it allows to post long text, it splits text into several transactions. https://www.myetherwallet.com is well known ETH wallet. It works in browser and allows to set arbitrary "data" field while sending transactions. You can try them out and share your experience here.