how moddable is sev?

i'm curious about how moddable sev really is because i consider to make my own mod (especially an ai mod). but since i'm not sure how promising such an effort would be i don't want to start it.
so i've heard about all those problems and bugs that players still have to deal with. just in theory, is it possible to fix current major bugs only by modifying the .txt-files and by using the parser-tool? (e.g. the bug with alliance voting)
are the current sys_ functions sufficient to make a good ai? and another question: if i understand it correctly the ai recalculates everything each turn. can i add new variables that don't have to be recalculated each turn such as the anger level?
maybe i'm completely wrong with this but my german sev retail version came with poor mod-documentation.