The people who enjoy being pursued by pvp builds in a trading ship are already in open. The people who do not would not suddenly change.
I've got no problems with incentivizing pvp for powerplay, but you simply can't force players to do something they don't enjoy, dude. Yes, powerplay absolutely should be different from the other parts of the game, but if you think you can achieve that by fiat, you'll be very, very disappointed. The net result for pvpers will be pretty much unchanged; no targets. Except powerplay itself will be much emptier.
And how do you know this? Have you ever talked to Powerplay haulers or tried it? Plus, you don't know how many would go for it from the main game either- its just you claiming to speak for the majority's behalf yet again. Go and chat to old Powerplay guys who left, or people like Ganksalot to know PvP guys like evasion and survival just as much as killing targets. Give people a structured reason to play and firm rules and they'll play.
At the very worst you'll have a more compact Powerplay with smaller Powers fighting over better systems under better rules.
Once again, if you want more people participating in pvp, you need to make them want to be there
So, having a structured reason (i.e. tactically) to haul for once (different to missions and the BGS) is not a decent reason? Plus, you are not forced to be one role- you can switch to how you want whenever you want.