Yea I would get a OKC but just breaks my heart to chop up such a nice bayonet. I have a Ontario M9 but would like a M7 maybe I'll get a nice one and keep it as is and a cheapo and hack that one up.
You can make it work for the 16 inch with a midlength or using the barrel sleeves for the carbine. You would not need to modify the bayonet.
I have one for a 14.7 upper and it fits on the crush washer and part of the flash hider but it is solid and works wonderfully. I would recommend getting one because it is fun to use and is something practical if you know how to use it.