Well, that's it. It's absolutely clear you have to pay for it; the question is - how much?.. Customized tasks are not available for fair prices. I'm not about "
something" - something to pay or something to work on. I work on
concrete things which I clearly understand and which surely will work for the end customer.
From your description, it's hard to understand what would you like to achieve, in general. That means, I should also work on the project specification for myself. Then I should code it. Then I should fix all bugs and support all the way conversation with you.
Now I either code the strongly specified task for the suggested budget or hourly rate which satisfies me, or I work on the project specification only, and other coders do the dirty job. miniBB is open source, so if you have only "fair" budget, you can hire lots of students or freelancers. I'm not sure why exactly "me" should work on it. I would wonder seeing phpBB or vBulletin team in action serving all customized requests for fair prices. I would develop for a fair price only if it would work for the miniBB as well, for miniBB community, too.
When we speak about "treating", for some reason, always only one side of the story is meant, "Customer -> Developer". I'm wondering when we start to think about "Developer -> Customer" chain as well? I think it's impossible to treat anybody well, if just the guarantee of the satisfaction is not provided in advance, and I'm wondering why it's being considered as "bad treating" or something. It's absolutely not on my end, it's only how you perceive it, reading my texts. If I would speak with you and tell you the same, you would feel another thing :)
Here is also good proof for your attention:
Currently, something to program which is less than $5K is out of my interest, and the price regarding small custom things is $50/hour. Regarding your addition, I would work it out for about $250 (if by now I correctly understand what it is about).