If World PvP were to become a thing, I agree somewhat with both of you above. Ganking in and of itself, alongside the current system of "raise at the saved aetheryte", would make ganking a very low-risk activity. What I would like to see is something akin to what Divine also mentioned, a "PKer" or "Red" player status upon ganking a non-red player. Many other MMOs have this - some call it the "Outlaw" system, for example. However, a jail system is just stupid. That would only annoy players that try to partake in a theoretical-then valid part of the game. MMO Jail systems are generally put in place for cheaters and hackers when it comes to MMOs, if the MMO decides to do that rather than just ban the player's account. This is not a fair "punishment" for loss in a valid game feature such as would be World PvP. Anyway, I think a fair level of risk for Red players would be that, for every target they kill in a given day (week?), their notoriety rises, and a bounty on their head rises accordingly. Every time a player with a bounty is slain, those who partake in the slaying get a cut of the bounty. Maybe it resets when they're killed? Naturally, the "red" status would be visible but not active when in safe zones such as the cities and towns. To avoid "town border gank-and-runs", they could even make it so the status does not disable in towns if you've killed a player within 60 seconds prior to entering the town. I don't know, but all of the details could be worked out.
This would make World PvP an in-depth and risky, but fun, activity. This would also add a sense of being a "defender" or "anti-ganker" or "pkker" to the world by giving people a niche to fill which would be that of taking out the reds.
I don't actively support World PvP, but neither do I actively condemn it. Not for FFXIV, anyway. It could be implemented, and it could be implemented in a way that is meaningful and fun. Likewise, it could just as easily be implemented in a way that it terribly disheartening and only open up the open world to ganking and griefing. If it's done right, I want it. But rather than having it done wrong, I'd instead want it to stay out of the game. It all depends on how they want to do it, if they decide to do it.