Maybe. To me what makes a guest character a good choice depends on two things: 1. How popular is the character...
I think the math for NRS is a little different.
Obviously you want some character who's going to bring thousands, if not millions, of fans, but they're already pretty heavily limited to IP's that don't mind seeing their character get torn in half.
With that in mind I'm sure some % of the operation is figuring out the expected return on the cost to acquire the rights vs the fan base it could attract. I'm sure they're thrilled to shell out $$$$'s for homelander because it's the SUPER rare cross over between mass appeal and hyper violence, but they probably paid a lot less for others.
With that in mind, someone like riddick strikes me as a "budget" choice they could throw in to round out a set of 3. The rights shouldn't be hyper expensive (up to the holder ultimately but lets just say their leverage is weak), and it's still got a nice and dedicated following to bring to the table.
Especially at this point where their list is getting smaller and smaller. There's some people have been hoping for (ash/pinhead) that aren't happening for whatever reason, but honestly it's not like there's a ton of viable candidates to choose from. I feel like the only other name i've seen floated that makes sense/could happen is Dredd .
There's lots of others that seem like good ideas (Laura Croft comes to mind), but I'm really not sure the rights holders are going to be ok with the hyper violence MK entails.
