If you take a secondary weapon with a pike or longspear it would make sense if it were a 1hander. As a frequent longspear user, I advocate them both being made 3 slot. (I even use a 1hander as a sidearm despite having only proficiency in polearms)
I think, though, an even more potent fix would be to make nearly every polearm unsheathable. From a support standpoint, polearms win out against other weapon classes. The selection they have available to them is also the most diverse... why should it be, then, that you can take advantage of that diversity on a near constant basis, by carrying a different type of weapon on your back? There should be a choice between good support while using a main polearm and a more one-on-one closeup fighting style.
Perhaps this would make hybrid polearms more common (for a 2hander to put on your back) but ooooh well, I don't really see speccing for diversity as a big deal, as long as there is an investment involved beyond picking the one class that has diversity available to it by default.
Side-note: since the bamboo spear is useable with a shield, keeping it 2-slot would make sense, since you could then carry a 1hander and shield with it. Its lower damage than a longspear and massively lower reach than either of the others don't make it as much of a problem, in my experience. I mean, it still has an overhead attack, how often does that really present anymore problem than the longspear does, in a support role?
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