X and Z to Y?

[Jeff the Green]

What happens if a character somehow has two effects or feats that replace a normal ability modifier to something with something else? Like both Keen Intellect (replace Wisdom to Will with Intelligence) and Force of Personality (replace Wisdom to Will with Charisma).

[Sword-Geass]

It depends on the wording:

If both say something along the lines of "you may replace your x with y" then you chose which of y and z to use, but only one.

If both say "use y in place of x" then you apply both y and z.

If they use different wordings, ie. one replaces, the other lets you choose, you would apply both, as you can choose the order in which you aplly things.

[Hogsy]

What happens if a character somehow has two effects or feats that replace a normal ability modifier to something with something else? Like both Keen Intellect (replace Wisdom to Will with Intelligence) and Force of Personality (replace Wisdom to Will with Charisma).

I don't know about RAW, but I would assume that you could either choose between the two, or if you obtained Keen Intellect before Force of Personality, then Force of Personality would simply have no effect, because you don't use your wisdom for will saves anymore. If however it doesn't replace wisdom but instead is added to it, then both would apply. Usually, it says if it doesn't stack with similar effects though.