Ok I'll start then.

I was thinking of having a few spell-like "En-[spell]" abilities. Each with a casting time.
Let's say: En-Fire I, En-Thunder I and En-Ice I.
When using one it does damage to your target, and gives you a buff for the next 45 seconds (placeholder number, I am not as well versed into balancing etc as some of you).
This buff will change how your weapon-skills interract with each other, or give them special properties.

For example: En-Fire reduces your GCD and ability cooldown by 2% per weapon-skills performed during duration of the effet (to a maximum of, say, 15% reduction). At maximum stack it makes your next cast instant (so you can instantly cast your next En-spell).