Saruman's economic infrastructure unexplained?

[Tuor of Gondolin]

Interesting comments, particularly Saruman's time limitations
and the suggestion (serious?) of a Sauron subsidy and
assistance, as is the related link.

How about this as a possible way of Saruman's
skirting around his economic/geographic limitations:

Even taking into account Gandalf's observation:

But Isengard cannot fight Mordor, unless Saruman first obtains the Ring.

What if Saruman had been successful in not destroying Rohan but
rather in using Theoden and Wormtongue to forge an alliance (with
himself, of course, as dominant figure---think Hitler vis-a-vis Mussolini
in relative power). With this de facto grouping he could very well have
also alligned with the realpolitik Steward of Gondor. If you posit the
Ring remaining lost wouldn't this military/economic bloc, with a
neutral Lorien blocking Sauron efforts to flank it, have been capable
of at least holding the east side of the Anduin? Then Rhovannion might
have become the disputed region of these power blocs. And while
orcs and Gondor/Rohan fighting together seems odd, recall the
U.S.S.R. and U.S.A./U.K. alliance in World War II. Mordor would have the
bigger numbers + oliphaunts, but the western group would have
superior cavalry plus Saruman's technology, including blasting powder.
Oh yes, and you have Gandalf, Elrond, dwarves, and Beornings and
Laketowners causing mischief in the north.

Just a thought.