I forgot to put this in my prior post, but if it required 2H proficiency to use...
Yeah, no.
Of course it would use 2h prof while in 2h mode. Logic ftw.
And if your build is a dagger build, and you want to do all your chambering, stabby stabby, etc, then why would it make a difference? You'd just take 2h prof instead of 1h prof, and wouldn't use a shield. The weapon would be functionally exactly as you are asking for it to be, while in 2h mode.