I'll cut right to the chase.
Instead of whatever current system is in place to determine whether or not one is in combat, what could be implemented is the following:
1. When in the Skill, Gear, or Quickslot menu a short countdown (5s) is started and once it's up your skills gear and quickslots can be changed freely, This count down is reset every time damage is incurred from any source.
2. Skills and weapons cannot be changed with the use of addons until they meet the countdown requirements. This is to prevent abuse by swapping sets etc. in combat.
Thoughts?