A concept that I've been toying around with for the past few years (even before the League was brought up) was that if mass-gatherings of warriors were to be held, that perhaps an "Interstate Warfare" set-up could be organized.

All the teams in two nearby states are gathered into two separate "State-Factions", that is each led by a General, who would coordinate the preparation and battle-strategies of this army, both before and during an Interstate-War.
In order to allow players to continue working with people they have already trained with, each team stays basically the way it is and is called a "company".
This solves the issue of mixing players around and ending up with groups that don't know how to work together as effectively as they might have.
So while a company may merge and fight along-side other companies, they will remain basically the same as always, except that the scale of their battles are much bigger.

The Generals would then work to coordinate the companies, while the team's/company's captain would coordinate the troops that they already know. This way the General doesn't have to keep track of the movement of dozens of individuals, but can focus on just a hand-full of groups, making their job less overwhelming and more efficient. This system would also keep the chain-of-command down to its bare necessities, without too much complication.

A possible positive side-effect of Interstate-wars is that teams in a state would likely focus more on helping and encouraging other people in their areas to start teams of their own or to join an existing one in order to strengthen their faction for the coming conflicts. Which would lead to a wide-spread increase in the size of our soaker-community.

These massive wars would likely only happen about once a year, after-which the state's teams would resume fighting each-other until next-year's Interstate-War.
Battles would take-place somewhere near the borders of the two states, so that travel time for both sides is minimized.
Wars could last for whole weekends, starting on Friday and continuing until Sunday evening.
There would also, now be a feeling of companionship between all the teams in a state, having fought, died and dried together in an epic war against a common enemy.

In order to remedy what is possibly the biggest problem with this concept, (supplying such a force) each person is made responsible for themselves.
They need to bring enough food, weapons, unfilled balloons, sleeping-equipment, etc, to keep them going for a few days. Special supply-depots could be set-up that are illegal to steal from or damage. Each player should mark or etch equipment with their name and phone-number in a water-proof ink.

This is just an idea and it would likely need lots of refining, but perhaps it could have a place somewhere in the league.