Based on a lot of ifs, buts and maybes but could we end up with something along these lines:

____________________McCallum/New Keeper

McGowan________Morris________Fojut/Souttar________Dixon

______________________Butcher/New Signing

_______________Telfer________________________Fraser

______Connolly_____________________________________Dow

___________________________Bilate/Anier

Subs from:
McCallum/Crap Pole
Souttar
Spark
Petrie
Paton
Rankin
Smith
Spittal
Erskine
J.Johnston
Muirhead
Anier
Murray
Moore

This is based on the assumptions that Rado, Nads and Dillon all deffo away.  However, I also reckon Butcher, Bilate and Fojut will leave as well (not starting a rumour on Fojut, I just reckon he might look to getting another club given the way things have panned out this season).

I'd ditch the 4-2-3-1 since we'll have Telfer and Scott Fraser and need to find a system to fit both of them in. Telfer doesn't appear to be able to play as a number 10 since he can't run in behind but is not tough enough to play as a defensive midfielder either. I'd go for a straight 4-3-3 as a compromise. Think the system from the 1st Scottish Cup game against Celtic but with footballers in midfield.

New signings? 1 goalkeeper,  1-2 defensive  midfielders, 1 young left back, 1 attacking midfielder, 1 winger (Johnston probably covers this though). Jackie or new manager got a tough job this summer.