The following is not a legal advise - it’s only for entertainment purposes 
If the job is a major one then seek a legal counsel to obtain the job. You’re right that the client’s request, as is written, is over-reaching and unreasonable.
The standards of satisfaction can be either subjective or objective. If the design can somehow be tested against a certain objective threshold, then maybe the client’s request is not so unreasonable. However, such an agreement should be very narrow - whether your design meest the client’s specific criteria, and nothing more.