Dutch,
This is a new twist that has me salivating, would love to see this option on all purchased clubs! Afterall, in real life, we take a slower more controlled back swing to avoid wildly mis-hitting the ball, why not here!
So for instance, the driver, or hybrid, or iron set, etc still has the same max ratings for speed, accuracy, spin, forgiveness, etc - but the user can adjust setting as he grown with them and gets used to them. Reduce meter spin a little, and accuracy goes up a little, etc. .Obviously, the max characteristics for the clubs can never be exceeded.
The only catch I see, is to make sure it applies to an entire round and can not be adjusted 'in play', so that it isn't abused. Similar ideas have been suggested before, but applied towards customizing purchases in the pro shop, not customizing the sticks once you own them - great addition to this theory, I'd vote to keep you on the island!