Bumping from the grave..
I just called WotC about this. In my game my player is playing a swordmage and wants to switch to 2h as a free action, attack, then switch back to 1h. WotC said that this is within the rules, although it's up to me if I want to disallow it. I think asked if it's within the intent of the rules or if it's a loophole. He said "it's not the intent and it's not NOT the intent. It's not a loophole either, it's a creative use of the rules". So I will allow it in my game. Also if a monster has an interrupt attack then I will rule that the swordmage is using 2h at that time and will not get the +3 to AC
I think asked if it's within the intent of the rules or if it's a loophole. He said "it's not the intent and it's not NOT the intent. It's not a loophole either, it's a creative use of the rules".
Ready is an immediate reaction, so immediate interrupts against that lower defense are going to be rare.If someone interupts you when you attack they use the lower defense, if not they use the higher. Punishing a guy for needing to drink a potion seems extreme.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.