The more pieces you have the more strong the effect is. Potentially change it so when wabbajack is boosting a stat it is reducing another stat. or have it so when the positive effect has occured the negative will occur straight after.
So effects can include:
1% chance to reduce your health to 10% of max health or increase max health by 50% for 10 seconds
5% chance to spawn a chaos creature that attacks everything.
etc.