The airplane safely flew for 9 years, at some point the paperwork itself becomes the problem, not safety. The FAA isn't perfect, by any means, but this just isn't something that should be any issue for anyone other than the repair station that did the initial install. An IA, on a subsequent annual, should be able to rely on valid 337s and other logbook entries from other mx professionals, and shouldn't need to take every 337 and logbook entry and validate every single aspect of the install. IMHO, the IA's job is to make sure there is an appropriate record for all installed equipment, but doesn't need to then go down the rabbit hole of checking the prior guy's work. In other words, IA sees an aspen; IA needs to ensure there is in fact a 337, etc. for the Aspen, but doesn't then need to go line-by-line through the 337 to ensure it's all correct; that was the first guy's job.