This I have already described saying that that part has already been planned.
Everyone interested will be told up front about the scale. And how it works.
everyone will be informed specifically on the reasoning and if disagreement happens we'll figure it out on a personal scale.
We're not trying to be unfair in any way.
I know how the process of making a video game possible.
All we had been able to gather thus far was that "If they didn't do enough work, or didn't meet deadlines, their payment was lowered." You didn't specify any details, so understandably, questions were raised. We weren't trying to antagonise you or appear patronising, it is just an area that could potentially cause a lot of grief so we wanted to highlight that.
A sliding scale like you're proposing is entirely different from usual collaborative "share of royalties" that you usually see. You can't just say "You will receive X amount, unless you fail to meet deadlines in which case this will be lowered." The fact that you've said "if disagreement happens we'll figure it out on a personal scale" leads me to believe that you don't have contracts in place.
I would love to believe that anyone that I got to work with me would be sensible and calm enough to just work through any issues with me. But when it comes to handling money like this it needs to be purely professional, and the process needs to be completely transparent. If you're going to be working with friends, then maybe it's not necessary, but you're hiring employees.
You have to consider:
How much the employee is going to be paid.
What circumstances will reduce payment. (Not meeting quality, not meeting deadlines, less than expected output)
How you determine quality.
What the deadlines are.
How you determine output.
How much payment is reduced for each criteria.
Who makes the decisions on reducing payment.
What the minimum payment is.
and more than anything, you need to ensure that the employee is aware of all of these, and that he agrees; This is usually where an employment contract comes in. Maybe you have everything planned for all of this, but from what we've read so far it seemed like something that needed to be pointed out.