I actually see good points in the suggestion. Baldur's Gate and other RPGs have this implemented and it works pretty well. For the use in PS I like to tweak the idea a bit:
- Base value for everyone is fixed at a certain value (maybe 30 or 50%) luck
- A special birth event or a specifc choice of race in the CC could raise that starting value for example for about 5%
- luck is not trainable but modifyable by spells, potions and items
- luck could affect looting, chances to successfully cast a spell, or avoid negative effects of different things; chances to hit or avoid a hit
- to balance it, i suggest to make it impossible to modify luck with multiply instances of one sort (multiple rings of luck plus necklace plus boots plus or multiple casting "greater luck" or whatever). So it could be only possible to higher luck with one ring plus spell plus potion. That also eliminates the +100% chances of finding magic items insanity like it is in Diable 2 (one could assume that the % are referring to the real chance, but it highers a given value for _that_ %. So with over 1000% (which is more or less common for certain chars) you don't get 100% probability of finding, but thats just a weird system imho).
- Also, for temporary raising like spells and potions, I can think of pretty big effects like raising luck for 10 or 15%, but afterwards for a certain time, lowering the luck for about the same amount. So you have to plan very well on when to use it. Also higher additional values might also wear off faster. For instance a permanent raise (like a ring) would only give a plus of 5%, while an extremely powerful potion of luck could raise the value for 20%, but only for 10 seconds.
With that system I don't see a problem with people abusing the CC as it is very clear on how the CC affects the value, neither I see a problem with abuse by being able to train it. If 100% luck are not acceptable even for a short time, one could cap it at 90% for instance. Eliminating the random factor at the "stats"-side, it also makes it much more convenient, streamlined, for people without removing the random chance factor at all. Also it doesn't mean that people can abuse the system better if the the mechanics are revealed (principle of open source

).