I suppose we can use a bit of crystal balling but I'm sure Nighty will be one of the first players picked, given he's a current International. I'm not saying it's correct but I believe 2017 will be his swansong.
In saying that, and if Dufty does play in 1st grade then our backline should look something like:
F/B - Dufty
Centres - Dugan and Milne
Wingers- McDonald and Nightingale
Mann will be battling it out with Hutch and co for a halves spot. Glymin needs to prove his fitness and over his hammy problem. Aitken should go to a utility role. Dodd should get a run if one of the above suffers injury or suspension. Even Isaac Thompson may get a go (lazy but has plenty of talent when switched on pretty slick and is a massive unit).
However, in saying all that, and knowing McGregor, I'm sure Lafai will be in there somewhere, probably at the expense of Milne (but I hope not).