For instance, your example (“a useful workshop facilitation methodology”) has as a primary goal the facilitation of a workshop. Thus you will be able to measure the effectiveness of your idea by evaluating the methodology in the context of a workshop.

In my opinion, the website (process) is a way to formalize the idea process, to think with “one head”, and to monitor and document the process in real-time.

Most ideas are conceived by a person or group of people based on 1) a problem to be solved, 2) ideas who have solved the problem, and 3) on the successes and failures or others. These are usually done informally.

The beauty of this concept is that every idea, whether it takes us to the solution or not, is valuable and tracked in real time.

You have given the proper basis for discussion. The next step is to conceive a more formal Design Specification document or, as you say, directly start with a simple blog or wiki.

The more structured you make it at the beginning, the easier will be to manage and expand it in the future.

The issue of authenticity (of user, date, etc) can be guaranteed by a digital signature.