Great idea first of all. Please allow me to make a few suggestions though.
Why not make 1 addon (that is aced) for all classes as autobuff did? I know your trying to keep size down in oreder to reduce lagg but i believe just a cahnge in logic would be able to do that easily. it would work something like this (roughly).
1. Check spellbook for all selfcastable spells or tracking and there highest rank.
2. List all spells in a window.
3. User then checks the spells he wishes to be automatically cast on any movement i.e. front, back, left, right, strafe left, strafe right, jump.
4. When said user checks the box next to a spell to be auto cast a sub menu pops up below that spell with boxes for Combat (in, out), always and rebuff time as autbuff's options are.
5. When the config panel is closed the only list of spells stored are those that had been selected.
6. For rebuffing I was thinking about using timex to time when a spells buff is either over or 5 seconds till over or 10 seconds whatever the option is set to. ( This MAY stop the problem of "Can't do that while sitting." ) I think if you were to use timex to check when a buff is needed you would cut down on used system resources.
This would allow any class to set up the same addon for themselves, any buff ever introduced by blizzard would automatically be able to be added (maybe even a popup asking to add a newly learned selfcastable spell to the autobuffing list). I think by doing it this way it would be a much more efficient addon and much much smaller. Oh yeah and did i mention it should definately be an Aced addon? got to wowace.com
Hm, it would be possible in fact to create a Util-based version of something like AutoQueue but with quite a different approach because without five minutes of testing that, I found numerous problems with it. I already have some approach ideas and I'd discuss them with anyone who wants to work on something like this. There are days when I'm really tempted but ...
To be honest, I don't have the time to do a project like this anymore but I would help out. I just thought I'd throw in my chips that this could quite easily be done by putting the Core functions in a Utilized base, much like I'm doing with the new BoogieBox AddOns.