I like the unpredictableness.
And isn't that what heavy clip hwacha, lochnagar flak/lumberjack and incendary gatlings are? It may not be as extreme as outright changing the damage type, but you already have such unpredictability in the game. Of course it won't be as unpredictable because you expect every hwacha gunner to bring heavy clip, because you should do that because everybody does and nobody on a gatling ever used incendary instead of greased, when they want the enemy armor down, because chem spray.
But if you can expect that and your expectations are the actual reality too than there seems to be a lack of diversity, but we maybe get new ammo types for more diversity, but if the new ammo types don't orient themselves on stuff that has never been seen before, which means more new mechanics, which maybe means tons of programming work, which means the devs will probably go for ammos with less new mechanics, which means we get the possibly new ammo types sonner, but it might be bad because there could still be a lack of diversity und unpredictableness, then there will still be a lack of diversity und unpredictableness...
If you imagine Poker, it's like if you had your hand and also a supplementary 2-3 cards where you could switch a card in your hand with a supplementary card whenever you wanted. Poker suddenly becomes very difficult.
I might miss-interpret this here, but isn't this what the gunner is supposed to do? Aside from the fact that you may already know all the enemy's crew loadouts, shouldn't the gunner make use of every single trick he has to make it as hard as possible for the enemy to fight back? I can understand though that you may not want a gunner to out-unpredict the enemy expectations for balance issues.