It's not easy to pick, but I think I'd go for something like this:
Marshall
Palmer Devlin McKenna Taylor
Armstrong Jack McGregor McGinn Christie
Naismith
1) No solid idea what shape to play those 5 midfielders in, but Jack sitting back and Christie in the hole behind Naismith would be a start.
2) I'm not convinced by Devlin, but given the options, starting McKenna's regular defensive partner next to him seems like a reasonable idea.
3) Naismith has to start and be given the captaincy for me. He's got great experience, loves playing for Scotland, and knows how to score for us. This young, underconfident, patchwork team needs someone like him on the pitch.