It depends on your personnel. Some teams use the weak side olb as a rush end, especially those with three larger linemen, a big olb, and three smaller, quicker inside linebackers. Jason Taylor fit that role.
When the steelers had 270 lb middle linebackers, they let the outside linebackers back off more and had the defensive ends rush to the outside, while the MLBs stunted.
More to your question, I have no idea how we can hide Kelsay out there, unless we rush him every down. He is slow, useless in space, and doesnt diagnose plays well. He is a good tackler, tall and takes on blocks fairly well. So in other words, he should be a left defensive end in a 4-3.
I predict he doesnt last long as the starter.