I think of ideas all of the time, and I'm constantly finding ways for other people to enhance them and there is no central way of doing this. How about a simple upvoting style with comments like Product Hunt?
Daily Hunt does this.
It's awfully simple. Every day, we have new ideas submitted by users. I decided to go for a bold UI showing only one idea at a time - mainly so people can focus on being inspired or absorbed in that concept rather than tens of ideas flooding their screen at once.
The plan, if it takes off, would be if there's any idea you upvoted that doesn't yet exist - and someone from the Daily Hunt / Product Hunt community builds it - they can know about it straight away. It often allows people to be more clear and understanding of their needs (by discussing it with others). Everyone wins, right?! (I hope so.)
A Medium post to accompany it: https://medium.com/p/3338436f15d4