Defending Rohan during the battle of the Pennor Fields

[Tuor in Gondolin]

OOPS! Of course, the title should say the PELENNOR Fields. Can't figure out how to edit the title.

In another thread Would Saruman Have been a Reliable Ally the subject of Rohan defenses after Theoden led his 6,000 to Minas Tirith.

Orogonally posted by William Cloud Hicklin
Actually I did mean setting out for Minas Tirith. Theoden could leave footmen as well as the old and young to guard the two fastnesses of Dunharrow and the Hornburg, but Edoras was left open; as Treebeard says (later), but for the Ents Eomer would have had no Golden Hall to return to.

Of course, there were apparently some 4000 Riders (less casualties, which would have been appreciable by then) who didn't make it to the Muster in time; these however would have been mere supplements to the garrisons

I'd be a bit more charitable on the forces left. Say 4,000+ with some 1st class fighters but the majority old, young, disabled, etc. But the women of the Rohirrim would fight well (not just Eowyn as an example, also recall how the women of the Wainriders held off attackers when they defended their encampments in an earlier battle, about 1,000 years earlier, in Rhovannion).

So how might an attack by Sauron's forces have been countered without immediate ent help? One possibility, split the bulk (3,000 or so of available forces) between the Golden Hall and Helm's Deep. As many as possible of civilians put in the areas between the Hall and Dunharrow, might be defended for a while. A long march with extended lines of supply and commuication would be necessary by sauron's lads to simultaneously attack Helm's Deep (and there would be a limited time (2 weeks or so?) to do so before some relief might come from Minas Tirith. 500-1,000 of the rest of the defenders could be used as a sort of horse infantry (using second or third tier quality horses) to loom around the northern frings of Sauron forces which would be attacking fortresses near the White Mountains. The Golden Hall and many dwellings outside, and some people, would be destroyed but many might be saved. I think Theoden implied some variant of his people, under Eowyn's guidance, surviving in such a way. As for structures destroyed, after World War II places in London like the House of Commons (and much of St. Paul's) were repaired/replaced). Why not do so with Edoras? Is such a plan viable? Any alternate suggestions to deal with threats sans ents?