I personally prefer mage myself.
Warrior is JUST behind, making a very close second, but I go sword-n-shield. I've never liked two-handed.
"Ideally" I like "magic knight" classes, i.e. mage/warrior hybrid; Arcane Warrior, Templar, Knight Enchanter, etc.
But that's just me.
If you go mage, Carver is the sibling who survives, so if you really don't like the mage mechanics, you can have him in your party.
There's also Fenris, another two-hander.
You would be missing on a few of the ability trees though; Hawke has the greatest amount of available skills and specializations.
So no "Berserker" or "Reaver", and the only way to get "Templar" is if Carver survives.
On the other hand, being a mage gives you access to Heal (always useful) and the Spirit Healer specialization.
That alone makes Hawke the best healer in the game, even better than Anders. So if you really don't like him, you can leave him be and still have a great healer in your party.
That, and mage Hawke is "canon", so if you're into the lore aspect, there's that going for it too.
In summary, if you've already played through as a two-hander, I'd recommend a mage for the sake of something different.
If you don't like it, you have two other companions that you can play as, and either way, you gain the best healer in the game, you!
Hope this helps.