Excellent post!

I have two comments...

If you fly overgross, you're breaking the rules. Where
will the rulebreaking stop? The answer is really nowhere.

I agree. But as you pointed out earlier, keeping within max gross won't
keep you safe, either. In other words, every flight includes making
decisions about performance that are arbitary, or more precisely, that
are based on experience. If experience didn't matter, why would we keep
log books? If the rules were enough, why would we need anything else?

You can study the design, and the available
modifications and authorizations, to determine
if it is performance, rather than structural integrity
of some component, that limits gross weight.

If it is structural issues -- which I would suggest it very rarely is
-- you'll still have a huge safety margin when 5% or 10% over-weight.
You are not going to be getting that close to the 'g' envelope, and
your landings are hopefully not going to be hard enough to be given 10%
of collapsing the gear!

Further, if you look at accident reports where over-weight operation
was a factor, I doubt you'll find many where structural issues came
into play. In fact, I can't recall reading a single one, and like most
pilots, I eat 'em up to try and learn from others' mistakes. As I said,
the failure mode that matters most is failing to fly, or failing to get
out of ground effect.