This rule makes sense. It's only fair that all characters start in their base mode, because starting out in your strongest form before the match would mean you have prep-time before the match. This rule probably won't change the outcomes of any of the fights in any significant fashion.It's no sense. Natsu will win. 90% fans consider him their GOD. "Natsu is most powerfull wizard in the world" bullshit.
He didn't do the shit even to Serena's corpse...
It's no sense how many rules there be - Natsu is beyond competition.
Natsu was in base mode versus God Serena's Historia, and to be honest they never really fought. Considering people far weaker than Natsu were able to take down the other Historia, I don't think Natsu would have much trouble. Besides, even as a Natsu fan I will acknowledge that he has strong competition from people like Irene and August. I wouldn't vote for his victory unless it's an accurate interpretation of what the manga shows. It just happens to be that as of right now, dragon force Natsu is arguably the strongest on Ishgar's side in terms of attack power. Natsu has his fair share of haters as well. I've seen people vote against Natsu simply because they didn't like him, favoring Mirajane or Wendy.