In terms of #4, I tend to like a version of it that goes something like 'choices and events which can happen during combat should be important enough to overcome most power gaps that are expected to occur in play'.

Personally I hate when systems use randomness to achieve that. I want it to come from cleverness and skill. The idea that 'I shouldn't be able to win against this foe, but I figured out how to do it anyways' is very appealing to me.

A system where I could essentially give the GM a script with some precomputed default set of actions and still do as well as if I actually paid attention doesn't really make me feel that it's worth playing out or paying attention to the fight itself. In such a system, the meaningful gameplay seems to me to be before the fight actually begins - making sure to only pick fights where your character build guarantees a win.

It doesn't have to be 'I could always lose' - even something where some choices end up being situationally more resource efficient or things like that it's enough. But there has to be an actual thing where me engaging mentally could improve the outcome in some form.