I understand your interpretation, I'm just disagreeing with your application. Look at it in these logical steps:
1. You must be a Swordmage to have access to the power. It's class-exclusive.
Half-right, half-wrong. You must be a swordmage to take Intelligent Blademaster (multiclassing makes you count as a swordmage for feat purposes). However, Intelligent Blademaster
is not a power, it is a feat, and even
if the swordmage class powers specified that they had to be used with a blade (which they don't, see below), as a feat Intelligent Blademaster has
nothing to do with powers.
Essentially, what you're arguing is the equivalent of saying rogues can't take Weapon Focus (heavy blade) because their powers are based on light blades, crossbows, and slings. Which is completely untrue.
2. Swordmage powers are based on the use of blades.
Wrong. There are
three, and only three, swordmage features that require a light or heavy blade:
1) Implement powers (if you want the implement's enhancement bonus)
2) The Swordbond class feature
3) The Swordmage Warding class feature.
That's it. If you're okay with not being able to summon your sword to your hand and losing the +2/+3 AC bonus, you can pick a bunch of Weapon keywords and build a swordmage using any melee weapon you want.
To me, that specifically implies the powers only work with blades and is written as such. The reason it lists melee weapon is because the blade requisite is already met due to using a Swordmage ability.
This assumption is entirely incorrect. As previously mentioned, Intelligent Blademaster is a
feat, not a power, and the two are not even close to the same thing in 4E. Moreover, look at the swordmage weapon powers. Notice how there's
no "Requirement: Must be wielding a light or heavy blade" line on
any of them? Now take a look at every single rogue attack power. Notice anything different?
Swordmages are not required to use a light or heavy blade for anything that does not specifically say it requires one. That includes Swordmage Aegis, it includes every single attack power in the book, and it
definitely includes the Intelligent Blademaster feat.