Well the best solution would be to give him a bigger wage and should he not hit targets, reduce costs improve efficency etc. he is hit with a penalty or reduction in the following years salary of foregoes any scheduled pay increase.
He should be paid for the job the bank want him to do, times have changed and people no longer except big one off bonus payments especially to bankers who everyone believes got us as a nation into the mess we are in. Hard to please everyone I know but that is what I would do.
Correct. A bonus should apply to money at risk where 100% of earnings applies to reaching a target, 110% etc for achieving better than target. It used to be held by management consultants that bonus should not be more than 20% of guaranteed earnings.