As I was reading through this, I found it interesting that the term "negotiator" was used more than once in a negative connotation, because when our DD went into a negotiator phase at age 3, we generally found it delightful. She's definitely a top-down learner, and we've always catered to that by explaining our reasoning for our rules. From time to time she'd ask for something, and we'd tell her no, provide our explanation, and she'd surprise us by coming up with solution that satisfied both of our goals... some of them quite impressive.
The only time this was an issue was when she offered something later for something now. A common example was when she was engaged in something at bedtime, and didn't want to stop. She'd propose skipping bedtime stories... a fair compromise that meets both our goals, as she gets to continue her activity, and we get to ensure she goes to sleep on time. Then we'd announce the new bedtime had arrived, she'd demand stories, and then behave as if we'd betrayed her by holding her to her end of the deal.
