I have tried to do this but the game won't recognize the icon banks past the 10th one.
You might want to look at the DarqUI Icon Bar which was built to mitigate this exact problem. There are 24 slots that can be set up with pretty much anything that can go into a standard hotbar. I have mine set up with all of my self-buffs, which frees up at least one hotbar for Ascensions. And since it has only my self-buffs, the window stays hidden 99% of the time.
I also use the hotkey save and load from DarqUI to save hotbar sets by Ascension name -- my hotbar #10 is reserved for Ascension spells in each saved hotbar set. I can load a hotkey set by whichever Ascension class I am running, without typing any commands. Take a look!
Image: DarqUI Icon Bar