My background before I learned Lua was, in chronological order, TRS80 BASIC, C64 BASIC, MS/PC DOS batch/command shell, PHP 4, tidbits of variants of *nix shells (tcsh, bash, ...), and just a good ability to read what some script is doing even if I don't know original construct.
So, since you have background, your 'addition' idea wouldn't be difficult. Shouldn't take more than a if/then comparison or two like I kind of outlined in my previous reply to your idea.
As for per player modification....well, that would not only take Lua experience, it would require a bit of experience with ULib and the UCL.
I don't mean to scare you away from it. It can just get complicated at times depending on what you're trying to do. Version 2 of this script uses so little ULib integration now.. it just looks up what group someone is in...then sets the limit multiplier if they belong to a predefined group or not.(1 if not)