I'm gonna offer a weird theory of my own.
Basically, I've always said that different weapon kits were made so that a main could have their choice of option for each Anarchy mode: one kit good for 2 modes, the other for the other 2.
Well if you see things like that, then mathematically, there are six possible choices of two game modes a weapon's kit would be good for.
The Ink Vac theory of special distribution states that for every primary weapon kit sharing a same special, no two combinations of expertise will ever repeat itself. There are 6 primary weapon kits with Ink vac and each kit works best on two different combinations of game modes. This theory applies for secondary weapon kits as well: no two combinations of game mode repeats itself amongst weapons sharing the same special on the secondary kit.
As for subweapons, weapon kits sharing the same subweapon won't have the same combination of expertise repeat more than twice. There are 10 weapon kits with Sprinklers, I do not expect more than 12 but I do expect one or two more as the SZ-TC combination has not appeared once.
Every time a new special has been introduced, both weapon kits meant to introduce it have had mirroring combinations. These combinations have always been SZ-TC/RM-CB until Triple Splashdown, a SZ-CB/TC-RM split.