At the moment 90% of PowerPlay is trade: take thing from capital to expansion system, take something else from control system to capital, and so on. There are just two exceptions: undermining enemy control systems and specialised CZ for expansion for certain powers.
I, like an awful lot of players, don't enjoy trade at all. I want to be flying a Vulture, FAS or FDL and I have minimal or no cargo space at all. This play style suits me and I'm not alone.
The result is that players of all the powers undermine like crazy, even when they're in turmoil, even when they're retreating and falling down the ranks, because undermining is the only consistent thing to do for combat players.
Every time I log in I get a "your power needs your help" message and I'm expected to take some commodity from my capital to some outskirts control system. I just don't bother and nobody else does.
So new idea:
Killing an enemy player in a control system: 5 merits.
Killing an enemy player in a control system in turmoil: 15 merits.
Killing an enemy player in any control or expansion system where they are wanted: 30 merits.
Killing an enemy player in your capital: 30 merits.
New NPC enemy agents in control systems (like the ones that interdict you constantly): 30 merits.
All turmoil systems should have Powerplay CZ in them where everyone earns 10 merits per kill - counting towards either undermining or fortification depending on allegiance.
This simple change would make Powerplay defence a worthwhile activity for combat players. It would also stop the crazy yo-yo behaviours of powers as more players undermine and expand than do anything else.
It would also open up Powerplay for combat players that don't want to grind trade.