So why not formulate a new rule like this:
Some cards allow you to use a particular skill for a specific type of check, or to use one skill
instead of another. (These cards generally say things like "For your combat check, use your Strength
or Melee skill" or "Use your Strength skill instead of your Diplomacy skill.").
You may only use one power that allows you to use a particular skill and one power that allows you
to replace the skill you’re using for a given check.
So you can use an effect that says "For your combat check use your Dexterity skill" and then another one that says
"Replace your Dexterity skill with your Wisdom skill". However, you cannot use an effect that says "For your combat
check use your Dexterity skill" and an effect that says "For your combat check use your Strength
or Melee skill" at the same time.