We sort of have Oyam for that, but I guess playing one or two copies of SK wouldn't hurt. I'm definitely going to end up updating the decklist in the future, this is just an early concept.
It's a good concept. My only 2 issues on Oyam is the discard cost and the number of monsters that can get over Oyam without suiciding (Brave Neos w/ Neos Fusion protection, Desperado, Darklords with their trap, etc). That's the main reason I see SK as being more useful, but I also understand it can be harder for some to get.
Small update/suggestion, consider using Counter Gate x2-3. With Yosenju running 3x DMF, smart players tend to attack with 1 monster in case of it when they can't clear backrow. Counter Gate offers an easy way to avoid damage while providing more draw power. I'd suggest replacing the Oyam and either Chalice/Tsujik with Counter Gate. It really worked well for me.