you could do something like this with the guide plugin.  Make a guide for each class and break it off into levels.  What you would end up typing is

!guide hox10
-  This would show spells from hox lvl 10

!guide tos
-  This would show all the tos spells

!guide tos26
-  This would show the spells that the tos gets at lvl 26

You could then make a !guide spells
By doing that you would get a list of the classes, then broken down by each level they get spells which could all be clickable, which would bring up whatever you wanted by just clicking the correct link in the popup.

it's not quite as nice as you requested, but it's something I could throw together in a couple of hours if need be.  I'm pretty busy this weekend and this week coming up.  But if no one else posts anything like this I could start on something like this next week.  It's the best I could personally do, and really isn't that hard to do.  If you wanted to help me with it so it can get done quicker let me know, if not I could probably have it done by next weekend depending on my schedule.

Either way I'll keep an eye on this thread, and I'll post something when I start it so two people don't do the same exact thing