Just that. While there isn't really a convenient place for it the main stat block there is a little room between your resistances and your hat. It wouldn't be ideal but it would avoid making any major changes to the character panel. Unless of course you developers plan on actually USING that sleeve slot.
This sounds like a good idea. As an alternate option regarding placement, it could simply be placed in the same section as resistances.
The placement is not a big deal, they can always add a extra ducktaped piece of paper that shows only when you have more than zero in Magic Reflection. I like the idea. I never know how much I have.
Unabashed jury rigging of the UI. I approve. The first time I got something taped onto my stats I lost it laughing.
Please. Do. This. The very idea of one of those little stat squares NOT appearing on my character sheet is terrifying. The very idea of seeing yet another character sheet improvised expansion makes me fret with anticipation.