Trait pages
Suggestion itself is good. However, there are balance issues to be considered… For one, if this was to be implemented it should be turned off in PvP and WvW.
Second, having several pages eliminates the cost to retrain your trait points at a trainer, well not completely but for the most part.
So, if this was to be implemented, this is how I think it should be balanced (PvE only of course):
Make a new NPC in each town or just in LA that can unlock extra trait pages for karma, perhaps from a minimum level onwards. Each extra page you unlock will cost more karma than the ones before it, up to a maximum of 4 pages total.
Switching between pages in town will not cost anything, but flipping a page while in a combat zone of any kind will cost karma. A randomly decided estimation is 10 karma per level, so 800 karma each time you flip a page at 80. And perhaps double that amount when inside a dungeon.