That would be really helpful
I certainly understand the developers reluctance of doing it as a "project" assigned to one individual. In the case of FPC, it seems to me that the FPC/Lazarus user community could "pitch in" cleaned up definitions and little by little end up with definitions that are as clean as they can be,
It would be rather nice too if the contributor included some simple program (in many cases a short console program) that would exercise the definition(s) being contributed to demonstrate the new definition(s) is/are correct. Maybe establishing some rules of how such specific contributions must be made would help. After all, it is a fact that there has to be - should be - one individual to verify and accept the contribution and, it's important to make that individual's job as simple and straightforward as possible.
The beauty of open source is that everyone can contribute and the aggregate of many small contributions often lead to a better result than one individual could ever achieve. I believe we should take advantage of that and create "structures" to submit and validate specific changes - such as API declarations.
Just thinking out loud...