It is a sort of house rule that I have been thinking about for some time now, but never gotten to it's realisation. Since I'm about to start my first adventure as DM, I was thinking of offering a chance to my PC's to improve their saves, and I would like, and indeed, need, some more info on this.

We all know that certain core classes(and PrCs) have one save that has good progression and two saves that have bad progression, such as fighters an rogues. I was thinking of offering the players who would choose such class a chance to get another good progression save base on their ability scores. How this would work you ask? Quite simple actually.

Say that player wants to play a wizard. They have good will saves and bad reflex and fortitude saves. Lets say that given wizard has 15 DEX and 13 CON, so he gets good reflex saves as well. This would represent that he trained his body to somehow overcome for his weakness. If he had 13 DEX and 15 CON he would get good fortitude saves. If he has the same scores in both abilities(say, 15 DEX and CON), a player can choose which saves he wants to have as good saves.

Alternative to this would be that the ability with worse score would get good saves. Thus, a fighter with 12 DEX and 8 WIS would get good will saves, again to overcome something he's bad at.

Both versions seem logical from some point to me so I would like some opinions on this. Will this broke the game? And it remains mystery to me what to do with classes that get two or more good saves, such as cleric, ranger, bard and monk.

So please, all comments are greatly appreciated.