We have only seen two autonomous weapons in the series (unless you count Tezca? I think he did some things autonomously), one of which did not use his wavelength, the other of which is a [i]Death Scythe[/i], meaning he'd be on a whole other level whether he was autonomous or not. Any weapon that is not a Death Scythe cannot use soul wavelength abilities without the use of a Meister, and only a select few Meisters can use their wavelength abilities without a Demon Weapon. 

There's a reason the whole Meister/Weapon thing exists, basically.