PvP done right would be a great addition to the game and would help it appeal to all the PvP ppl out there, PvP done wrong would destroy most the game and why a lot of people came to FFXIV to begin with.

And I think it will take alot more then most people realizes to make PvP effective and worthwhile, without forcing people to do it for gear or unbalancing PvE abilities for PvE use.

Here are the issues I see.
-If they do not balance abilities PvP will be unbalanced to the extreme. (aka thurm can solo the world NMs, good luck killing 1 in PvP)
-If they balance abilities for PvP they just horribly nerfed PvE which will cause an outrage. Example being able to do a 1500dmg attack might be overpowered in PvP it is not in PvE where the mob has massive amount of hp. SO drop it to 600dmg for PvP and you just completly nerfed Archer in PvE.
-If they do not give huge rewards (gil, sp, or armor) people will see it as pointless and will not do it. (ballista in FFXI)
-If they add the rewards that make it worthwhile the PvE people which made up the majority of FFXI will rage over being forced to PvP to get the best gear.

I really interested to see how SE addresses this issue.