I agree with many of your points, but not this detail: the "Wall" is a giant cliff/ravine stretching from the Manetherendrelle to the Jehannah road, hundreds of feet tall. It's impassable, allowing Ghealdan to push back invaders by holding the Jehannah Road (as we know, south of it the area is thickly wooded and has north-south ridges making it difficult for armies to move there.

They cannot build roads north of the Jehannah road, and that road itself between Ghealdan and and Remen is a difficult position to hold, and to take in the first place with the Seanchan being in good defensive positions north of the road.

There's not much Andor can do for Ghealdan's protection, without channellers and Travelling, or stationning a huge force (and one that can face damane) in Ghealdan itself.

Stretching itself thin by occupying and fortifying the stretch of land that nominally belongs to Altara to the east of Murandy may not be so wise now that the Seanchan can Travel and can easily surround this defense system, or by-pass it altogether.

Andor's current position isn't that great. It's caught in a battle with the Shadow at its capital, the details of which (e.g.: which of Elayne's forces are still there?) and the outcome of which could change many things for the long term. There's Murandy to the South, with the King having an army he will have to bring to war soon or risk lose control of, that's never been a friend or ally of Andor, and that is no match for the Seanchan should they decide to invade either. Some of its cities important for its economy are very isolated (Baerlon) and Whitebridge isn't in a much better position - easy to grab for foes who can Travel. Elayne probably has the allies and the forces to hold Caemlyn and Four Kings a while, but the Seanchan might not have much problems making Andor shrink back to the borders of Ishara's times, without the west and much of the south. Far Madding itself can hold, but they don't have the forces to prevent the Seanchan from taking the Hills of Kintara if they wish, and cutting Andor's mundane routes to the South. Another major problem is that the BT makes Caemlyn a major strategic target for the Seanchan. This is turning into a huge security problem for Andor (in more ways than one), and the fact Elayne herself is Aes Sedai is both a boon and a danger for the nation's security as well (the Seanchan hate channellers, but there's nothing they hate more than channellers who hold power. It's "AS" rulers like Elayne they have faced in the Consolidation.).

It's hard to see how Elayne could possibly make the protection of Ghealdan a priority any time soon, unless massive changes are coming either as some kind of diplomatic resolution of the Seanchan conflict that one way or another will change the situation of Ghealdan and Andor a lot, or because Egwene's hopes of an alliance of all channelers comes true, and they commit themselves to war against the Seanchan.

But for now the fact the Seanchan have Travelling really has changed military planning. The nations can't really rely on geography anymore to establish their defense systems. Anywhere in the world a Seanchan army can suddenly appear out of thin air.

If not for TG, the time would be ripe for the anti-Seanchan forces to get their act together and strike at the heart of their forces to eliminate them before it's too late.

Post TG, if no diplomatic solution has arisen yet, it's going be a decision to ponder, depending how their forces of everyone still stand by then.