If OV walks, you could keep Coples and Wake LDE. From there, DE becomes the highest need in the draft which I think you could get a good one in the draft. I love Shaq Lawson and watch Emmanuel Ogbah shoot up draft boards.
My issue though is where do you find a CB good enough to start? FA? 2nd round CB? Do you draft a CB in RD 1 and hope a starting DE is there in RD 2? Where do you find your LB's? Yikes....Got to bring back OV. Keep your own.
There are too many holes period, but you go defense first 3 rounds most likely in the draft. If we get a top 5 pick like you are thinking (I don't think we get that high) we should be able to get two really good pieces for the defense at least....