As someone with chronic altitis, one thing I'd love to see is a simpler way to add/modify multiple enhancements.
For instance, being able to click on a power and then selecting 2 End Red, 2 Acc, 2 Dam in the same way you'd use an online shopping cart, for example-you get a popup box with a list of all the basic categories and can enter 1-6 of each then click "OK".
Also, the option of selecting IOs (not rares, just regulars) as the default Enhancement type.
And since I use your fantastic planner every time I load up CoX to remind myself what powers/slots I should be selecting when levelling up (rather than respecing) maybe a "level slider" that lets me slide the level of the build (and only the powers and slots I have at that level) down to whatever level I'm currently playing at, so I'm not confused into thinking I should have powers I don't have. (I understand most people are smart enough to figure this out at a glance, but even simps like myself deserve a little help now and then.)