I think the focus shouldn't be on whether such syntax is possibly confusing or not because
a) People will always remember that's either one way or the other, but are
very unlikely to just assume one; hence they can always check what it does, and more
importantly,
b) It's actually pretty easy to remember which way it is, by just considering that a
syntax feature exists for scenarios that can't be easily solved otherwise. For for
... else it's actually more tricky than for the proposed syntax because that
doesn't let you distinguish between "else is only executed if the loop didn't
break" and "else is only executed if the loop didn't execute at
all". But for for ... except or while ... except it will be
even more obvious because try ... excepting the body is just as easy as,
well, try ... excepting the body; it's pretty clear that no new syntax would
be required for that and hence it must concern the statement itself since that's not easy
to work around.
The only possible confusion I see is when people look at something like this:
for ...:
LENGTHY BODY
except ...:
HANDLER
else:
SOMETHING_ELSE
and only look at the except ... else part and readily assume that the two
are complementary. But that's easy to prevent by only allowing the opposite order, i.e.
for ... else ... except, stressing that the two are unrelated in this
case.
In the end a feature should be driven by its usefulness to the community and whether it
provides a solution for an otherwise (hard|awkward)-to-solve problem. I could imagine that
due to the awkward workaround, especially regarding with, corresponding
"self-made" code is either error-prone or people will not even try to work around it in
the first place. This feature will probably be among the less prominent ones, but someone
who needs it will be glad that it exists and they're also likely to be well aware of what
it does (just like with for ... else). Someone who encounters that feature
for the first time, e.g. when reviewing some code, will probably check what it does and
even if not, the assumption that it excepts the whole body should be
perplexing since (a) excepting whole blocks by default is not really best practice and (b)
it's pretty easy to accomplish that with existing syntax.