This might need some lateral thinking. You can choose negative traits based on the mutagen you intend to take. After all, if you will have them anyways you might as well think of them as free points when they are countered by other traits. It may also be possible, yet I don’t have proof, that you can do something similar with positive traits. If you wish to remove glass jaw or bad back, you might have a bad time just using purifier. Their counters can be limited, difficult to get, or only in the starter set. The trick is to use the purifier to not only have a chance to get rid of bad mutations, but to have a chance to reclaim the mutations that also counter those bad mutations. Toughness and strong back are two traits I use to that effect. Preference should probably be towards traits that can’t be easily included through mutagen.