yes because we know this for a fact....oh wait, your just making assumptions based on FFXI. Hell we dont even have HNMs yet...we may never get them for all we know. The pets stats...again should be added as part of yours, making in whole, what it would be if you didnt have it. Also it would be very easy for them to let you control what the pet does by adding its skills to your bar, so you dont have to worry about it doing what it did in FFXI by you WSing and it using the wrong breath type.
until you have seen it done in some form of this game, you cant sit there and say it would be unbalanced or suck, because it does not exist in any form to compare it to.