For those of you with the becmi/rules cyclopedia, I will begin recommending changes to the rulebook.
Recommendation one: the saving throw.
Rather than change saving throws according to the class/race progression tables allocate +2 save points per level. The player may allocate these points as desired amongst the five saving throw slots. Now you may pour them into breath weapon to become that dragon slayer increasingly immune to breath weapons. Your poisoner might become immume to poisons.
How to use: the new save is a dice check on a DC(20). The bonus in the relevant save slot is added to the dice roll and any result of twenty or greater is a sucessful save.