Yesterday I was playing GWEN and defeated a boss. I went to capture and found that the elite skill is something from factions, and was not allowed to capture the skill. This irked me a little bit. I was thinking it would be nice if we were allowed to capture the skill, but just not use it until we paid for either Factions or Nightfall, whichever campaign the skill came from.
This may be something unique to GWEN as the bosses are allowed to use skills from all three campaigns, I'm not sure if the rest of the elite skills are exclusive to the campaigns they come from or not.
Thoughts and ideas?
EDITS
OK, It seems people aren't fully reading my above comment so let me make sure I'm clear. I am NOT suggesting that I be able to USE the skill that I'm capping, just that I'm able to cap it. A character wouldn't be able to use a skill until the appropriate campaign was purchased. Please, no more comments on having to buy the campaign if I want to use the skill, I understand the need for this.
Summary of valid problems with this proposal
Problem: People would unknowingly cap a skill that they could then not use because they don't have the campaign. (DarkFlame)
Response: Something could be added to inform a player they are about to capture a skill that will not be usable until they purchase the correct campaign, and allow them to cancel the capture.
Problem: Anet will lose money (Miska Bow)
Response: As long as people still have to buy the campaign to use the skill Anet will not lose any money
Problem: When would the xp for the cap be awarded? (Hiken Trilear)
Response: If it is easy to implement then it would be extra incentive to buy the campaign if the xp is awarded at purchase time of the campaign
Problem: A very low percentage of people would actually take advantage of this (Kanyatta)
Response: That's why I started this thread, to get an idea if there was enough interest to warrant action.

Problem: What's the purpose in capping if you can't use the skill (Various Posters)
Response: Mostly a time saving issue. (Please read my responses to Kanaytta, better detail there)