Dixon is 20 and I think would be fine as a 2nd choice (or 3rd with O'Brien playing there currently) right back.
Armstrong should be in the squad, rotating in/out.
The savings here as 'squad players' would mean we have a lower number of signings required.
If were looking purely at 3 starters: CF, RW, RB and 4 rotation players: RM, LCB, LB, GK then if we use the loan market effectively we 'may' be able to target an additional CM player.
I suspect, knowing Moyes track record we'll go for a smaller squad but hopefully TFG focus on signing youth and quality.