Warlord Traits for 5th Ed Codexes

Listening to Deepstrike Radio's coverage of the Dark Angels Codex tonight got me thinking.  Basically they were talking about Warlord Traits and how they can be completely useless for every 5th Edition Codex out there if you are rolling on the chart in the basic rule book.  Locally, we have a house rule that you roll your d6 and then pick one of the three options available on that roll.  After this show I'm thinking about proposing a new house rule to the group.

I'll be honest, nine out of ten times I don't even care what Warlord Trait I get because they do absolutely nothing for whatever army I'm playing but here's a possible way to make them worthwhile.

If you are playing a 6th Edition Codex (Chaos Space Marines, Dark Angels or Chaos Daemons) this will not apply to you since the same idea is already in place in each codex.

If you are playing a 5th Edition (or earlier) Codex and your Warlord is a named character, you can "pay" 15 or 20 points (need to nail that part down) to choose your Warlord Trait.  This will need to be done prior to the beginning of the game and before any dice are rolled.  You are still using the Warlord Traits from the basic rule book.

What this would do is allow for you to customize your Warlord to fit your army a little more.  Since only named characters in 6th Edition Codexes automatically come with a Warlord Trait, I figure it should only apply to named ones in the 5th Edition Codexes.

For example, prior to showing up I could choose to add 15 (or 20) points to the total cost of Asdrubal Vect for my Dark Eldar and give him Night Attacker, allowing him to cause Night Fight to automatically happen on turn 1.

I think the point addition would be fair.

You could, of course choose not to take the named character or not pay the extra points and roll for the Warlord Trait as normal but again, this decision needs to be made at the time you are building your list.

Let me know what you think of this and if you have any suggestions of how many points should be added to the total cost of the character model.