I'm afraid I'm not a good enough logician to answer your objection properly, but there are, I believe, credible approaches to doing mathematics on a countable carrier set, for example:
"Credible", likely yes. Likely
also awkward. To weasel out,
I just said we "want
completeness". When you look
at the alternatives, you may
conclude that you still want
completeness and, thus, are
stuck with the reals with no
alternative you "want"!
> The get out clause is that they are not a set, but a class.
Good grief! In axiomatic set theory, introducing
'classes' was the "get out clause" from
the Russell paradox of the the set of
all sets that are not members of themselves.
So, the patch, the time I studied one version
of axiomatic set theory, was to say that
there are some sets and we know what they
are and we know that the Russell paradox
can't happen now, so let's go on.
It appears that the OP and alternatives
to the usual treatment of the real numbers
are based on what can be described.
This issue doesn't impress, or, really,
concern me. To me, for just an easy answer,
there is the real line with points,
and that's description enough for me.
Apparently the OP wants a description in terms
of digits and is bothered that
uncountably infinitely many reals need
countably infinitely many decimal
digits to be described. Okay,
if don't like all those digits, then
just return to the points on the line
and let those points be the description.
Good enough for me, but at this point
I have quite different fish to fry
getting my business going, really like
the real numbers and what classic
pure and applied math do with them,
and see no good reason to change
the foundations of what I do.
More generally, it appears that
computer science is struggling to
find something to do beyond
the biggies of quicksort, heap sort,
merge sort, AVL trees, red-black trees,
BNF, YACC, LALR parsing,
relational database, P versus NP, etc. So
computer science wants to
take parts of statistics, optimization,
control theory, and now the foundations
of math for its own and, in those fields,
do things differently.
Maybe I'm missing a point: Maybe
the idea is to have all the
'numerical' data computing works
with be describable in some
finite way, that is, not just
a countably infinite sequences of
digits, and, thus, get rid of,
say, numerical error. Maybe.
Seems a bit far fetched.
http://arxiv.org/pdf/math/0509245