The feature I wrote out would allow for this to a degree, due to the RAW difference between holding and wielding a weapon. While a kreen needs an extra hand to wield most weapons, that's not true for holding them. This means at the extreme end of the spectrum, you could "hold" a bow with one hand while you weild a glaive with the other three, then switch seamlessly to the bow without a weapon draw. Shields muddy this up because of donning and doffing.