Since the idea of OSHW is an extension of (F)OSS and gaining traction a fair bit later it might prove worthwhile to draw inspiration from what the community around (F)OSS is doing. And guess what: They don’t just pretend the problem isn’t there.
In the following it is assumed the certificate is and remains a form of self certification.
Regarding penalty: It seems certain that abuse of a registered trademark, that everyone may use under the condition of meeting specified terms, can be ordered not to continue and cover the cost of proceedings by a court of law.
It appears very likely that for the duration of time where this abuse took place the offender can be ordered to either reimburse the vague damage, pay punitive damages or a sum that is laid out in the conditions mentioned above. This could help finance the OSHW movement and provide an incentive for proponents to check users of the trademark for gross violation of the conditions.
It could even be part of said conditions that someone, after self certification, has the obligation to register the project. Failure to do so would already constitute a violation and be grounds for the penalty stated in the conditions which, in doubt, could be basis for financing the review process of the individual case.
I do not believe the average user or general public does (yet) care enough about OS to show any interest or reaction in or to a list of shame. Individuals with such preoccupation then again need less than a minute to sniff out all published documents and arrive at the conclusion that vital parts needed for reproducing the hardware are not provided. Such list could be very valuable regardless. Especially when dealing with openess first and foremost one would expect all information about proceedings of any kind to be documented and publicly available. This way members of the community and public could review cases and acquire understanding about the standard to which certification is held in practice and also check for consistency in treatment of cases.
The idea of having a form of any kind which users, who have a suspicion, can use to report projects for review would definately be valuable. This would naturally corellate popularity of a suspicious project with chances of review. It would also prevent tunnel vision of a few who would otherwise contribute leads.