I find it amusing that you use the word "standalone" to describe "ace-addons", as the very definition of "ace-addons" is that they make heavy use of libraries to share code amongst themselves.
I find it sad and ignorant that you limit yourself to Ace-based addons, as there are many great addons that are very well-written that do not use any Ace libraries. Do you have any technical understanding of addon programming and libraries that would lead you to make this decision, or are you just going off some forum posts by ignorant loudmouths that said "Ace makes addons better"?
Anyway, look at FuBar_RegenFu for your current regen rates. I don't know of any addons (Ace-based or otherwise) that only track mana gains; some combat meters (such as Recount) include mana gains, but I don't think any of the include your "natural" gains from spirit and mp5.