Thanks. It does makes sense that this is a kikuchi yari with a shortened tang. It does have all the hallmarks: shortened tang, form-shape, length and the history of this style yari being a likely candidate for alteration.
I've added a few more images. Maybe they can provide more hints as to the age. I am speculating later than Nanbokucho. But then, perhaps I'm basing that on what it is now, a yoroidoshi, as opposed to what it was originally, a yari.