there are ways of creating balance, given the correct situation.
taking a script which is not game mechanic altering, but has very powerful function can be balanced by cost (one time or over time),
scripts which take some aspect of the game and automate it in some way(take ware price monitoring, as this is something ive been paying attention to recently), this can be balanced (in a manner of speaking) by making it inefficient, more beneficial for the player to do it himself. (a hefty price tag also xD)
So in that respect. adding scripts should not be a problem, as longs the scripts function can be adjusted for
As for which scripts to add, i said this before, everyone has different 'holes' in the game, and theres a lot of scripts which fill these holes. the content should aim to fill as many 'holes' as possible. in other words, anything that sounds good
Modifications are a different story and are, unfortunatly, outside of my expertise.