What I am seeing is an attempt to keep things too complicated.
The issue seems to be the players want to keep the combat complicated, when the reality of the game is that it is all fair enough when either no one can pull off these maneuvers or everyone can. The only reason to really have rules for detailed moving in combat is to micro manage the combat, when standing there hacking at each other is just as likely to come up with the same end result.
I agree flanking and such moves can be critical in an rpg combat, but only because you make the combat rules that complex/realistic. Being more abstract/simplistic doesn't necessarily change the final outcome, it just streamlines the game mechanics process for getting to the end result. The biggest variable in rpg combat is the lucky rolls, with stat and level modifiers coming in second.
So I would just settle such questions of flanking, moving around behind, etc.... by doing a simple opposed roll. So if they succeed the CK gives a bonus of some type, usually +1 or +2, to their next attack/AC/whatever, based on what outcome the player was trying for.
I know you wanted simplity out of C&C, but if you let the players keep adding more and more house rules, you won't be very far away from 3E.
Importing feats or skills are not necessary. Just figuring out a reasonable and predictable (by the players) opposed roll system modified by not/being prime, stat bonus, and level bonus, will cover most feat and skill type situations. Is the mechanic behind all of this being spelled out by lists of feats and skills? No. It is being resolved in a fair and equitable manor though.
So, because of how detailed your first post is, I get the feeling that your players don't like having such general and abstract rules that are perfectly capable of achieving the same end result as the detailed lists of feats and skills 3E has.
So I suggest you just use the oppsed roll or TN system as is, and give written examples (preferably common ones) for your players to refer to and get an idea of how to expect you to use the rules in situations that are not spelled out in black and white.
Eventually, I think everyone will realize that everyone can do everything they could in 3E, but it won't be determined by feats or a skill system. It is determined by a much more abstract system that is modified primarily by not/is prime, stat modifiers, and level modifiers.
Thinking/refering back to 3E feats and skills to realize what you can do with a system as abstract as C&C is all well and good, but to create house rules that make C&C just as rules laden as 3E is not good.