I wouldn't "bin" anyone. If some of the players out on loan got offered a contract and thought that their careers were better served moving away I'd let them go but otherwise I'd keep hold, they're young and look promising for the future. From your out list providing they recovered from their injuries there's no way I'd let Penky or Platt go, both have been excellent this year. Maden is retiring anyway that's no secret. Aspinwall is getting on but has played well before he got injured, can see him moving more to being cover, playing in the reserves and taking on more of a training and coaching role rather than a 1st team playing one though. Beaumont looked very good but disappeared, now he's come back and done a season out on loan if he's proved himself (not seen him play properly sure Rowley has) I'd keep him. Pitman looked very good last season but not quite ready for the level we want to be at (could be in the future) but more than good enough for The Championship, can see someone coming in for him & him taking his chance. Same with Walker really, bit the Alex Brown of this year, came in with some fanfair but never really clicked in the team, went out on loan and did well elsewhere.
If we go up to SL I'd just look to add, with an extra £1,000,000 central funding and £0.8 million salary cap we can add players around what we've got and build a squad with cover in every position. If we don't go up then well I can't see us being far off, we've recruited over the course of the season and are still short of the £1 million salary cap, I don't see a lot of change needed.