Is there any way a verminous hunter or a druid with a vermin companion can reduce the size of their companion? I don't believe reduce animal would work because they are vermin, and reduce person is not on the druid spell list so share spell won't work.
And if you have replaced shared spells, the "Carry Companion" spell can serve as a backup. It's second level, but you can get a scroll for emergencies.
Also, if you have share spells, you can "reduce" your companion by casting alter self on it to turn it into a small or medium humanoid form, assuming you have the ability to cast the spell.
Any way I can extend the reach of a verminous companion without changing its size? The spell "long arm" isn't on the druid/ranger spell list and it can't use longarm bracers because I believe they require activation.