I think "Form of the Dragon I" is being underrated. The only true limitation to your spellcasting are spells that require material components. Everything else is valid, so I´m not sure why is it so lowly rated.You also loose all your gear and weapons when you take this form. A magus without his weapon is giving up a lot of power and nearly all his crit chance.
Isn´t it possible just to drop the weapon and pick it up? I mean, I think I read somewhere dragons were capable of wielding weapons? Or am I confusing it with something else?