My two cents...
This is probably too hard to code, but it seems like a grappler should have to disarm someone with a knife before grappling them. Otherwise they are in for a whole world of hurt.
Let me rephrase that. If the grappler does not disarm the knife wielder, they should risk getting stabbed, repeatedly. A person attempting to put someone else in a choke hold has given up trying to control the limbs, simply due to the mechanics involved in choking someone out.
I think that if you talk to anybody who has trained to defend themselves, it is almost universally acknowledged that a choke hold is one of the most dangerous moves out there. If you get locked into a choke hold, you have a few seconds to deal with it before you're out. On the flip side of the coin, it is extremely risky to put someone into a choke hold if you don't have full control of the situation e.g. They don't have friends around who are going to beat the snot out of you, they don't have a weapon, etc.
The choke hold is like the kamikaze attack of the unarmed world. If you don't land it, you're probably in a whole lot of trouble. And it's not usually something that you lead with, unless you have a huge strength and/or size advantage over your opponent.