Well as far as I know, Paypal doesn't check what the money's being used for if it's from one account to another. Alternatively, I'm sure there are other payment methods.
As for goal reaching/lack thereof, we could institute a simple system. Option 1. You get refunded your donation. Option 2. You keep it in the "bank" for the next thing you vote on. Option 3. You keep it in there for general usage (aka, it goes towards the next scanlation regardless of whether you vote on it). How do we determine what gets scanlated? Thread on the forums. People vote. If you vote for something, you pay into the fund for that scanlation.
User 1 votes for Alice.Tahakarabo.
User 2 votes for Alice. Blood.
User 3 votes for Alice.Tahakarabo.
Close polls at the end of the week and lock them.
If you voted for the winner, you pay into the fund. If not, you don't have to. Does this mean only certain doujins will be translated? Yes, yes it does. Personally, I see some as better than none.
On the "how do we enforce this" policy: Set up a hypnohub email. Someone sends a payment to the paypal account, then sends an email to the hypnohub mail saying "Hi, I just donated $X.XX", easily confirmed given how the payment will show up on paypal.
On trust. Well, I can't honestly say I know how much goes into scanlations, but I think that in this scenario, 1 fuck-up means kapootz for the whole thing and I doubt people would be fronting more than $20 a pop, so it wouldn't be a massive hit. In addition, I don't believe Mindwipe/Vanndril would do that.
I think the biggest question is something like work ethic/willingness. The system I've proposed puts a lot on the admins. In the event that the doujin doesn't get funded, it's their responsibility to get the money back to people.
As well, even if it was decided that this was going to happen, I think the site's PM system would need to be restored first.
Thank you for reading.