I agree that it is impossible to remove all ambiguity, that's why we have the Q&A (and why every other sport has one too). I don't agree that lawyers necessarily have to be involved. Or more specifically, it doesn't have to be lawyers that proof and edit the book for precision but there needs to be another layer in the process.
My understanding of how the rule book gets written and updated is that the rules committee first collectively create their list of prospective changes and goals, then discuss/write/re-write amongst themselves for months maybe years. Once they reach a certain point, perhaps during the year before an update, they get PDGA staffers involved in the discussion (Big Dog, Downes, etc). Then they finalize everything and give it to the board, and the board votes yay/nay on each rule/change.
I think that's too insular, and the extra layer I would add is a collection of TDs/players (maybe 20-25 in total) who get an early look at the rules and whose task is to comb through everything looking for the ambiguity and the potential loopholes. Essentially doing exactly what happens on message boards/social media and at tournaments in general for the first 6-12 months after an updated book is published. And their feedback would allow the RC to fine tune language they may not have even realized was imprecise, and do so before the rules are officially published and put into use.
I think too often rules are added or re-written with too much institutional knowledge baked in. By which I mean to correctly interpret what the rule intends, you often have to know what it used to say and fill in the blanks where that language or intent has been inexplicably removed from new wording. Or if it isn't an old rule/wording, it's a discussion had within the RC of a point that they know and understand but fail to include unintentionally.
The TL;DR version would be...they need more fresh eyes proofing the rules before they publish them.