Merrilor isn't really about gathering the Light's armies IMO. Or about the Seals really, those are just the lies that Egwene tells herself to justify it in her mind.

Merrilor is about the Amyrlin trying to seize control of the nations from the Dragon Reborn. Rand knows this and has set Egwene up. The only people who will be invited are people Egwene thinks she has a good chance of convincing to turn against Rand for her. The Asha'man wont be invited and Rand will bring only a token force himself lest he make Egwene too wary to confront him openly and publically which is what he really wants from her. The dream she had of the great crystal sphere held together by ropes is about the White Tower, whose authority over the nations is about to be shattered by the return of the First Among Servants.

Or at least, thats what I hope will happen. The five hundred Asha'man under Rand's command at the moment will likely be on standby, ready to gate in should things go pear-shaped and Egwene actually succeed in her powerplay.