Assuming, if we do go up, we'd keep playing the 3-4-1-2 (maybe 352 with a flat central midfield 3 for tougher games?), I'd like to see us sign:
First choice GK: preferably Deano, on loan again more likely than permanent, but permanent would be fantastic!
First choice RCB: honestly, I'm not too sure about this, I reckon Bash would step up a fair bit better than most people expect him to - but I could see Wilder using Bash more often as part of a midfield 3 (flanking Norwood, like he did against Leeds away this year and Pigs away last year). If so, we'll definitely need a new first-choice RCB, and I'm going to nominate Reece James (loan) here. Admittedly, I haven't seen Wigan play much, and I know he's been playing either as an RB or CM, mainly - but he's a decent height (6 ft ish) and seems to be a good player both offensively and defensively, so I reckon he would adapt to the new position and suit our notorious overlapping centre-back system quite nicely... I'd also offer Cranie a year's extension as back-up, because why not?
Back-up LCB: not sure who to suggest here, but since Kean Bryan has barely played, I assume we'd sign someone here. They'd have to be left-footed, and have to be content playing second fiddle to JOC. Any old-hands with PL experience that fit the bill? I'll put forward Maxime le Marchand - plays for Fulham, who've had an awful defence this season, but this guy's looked pretty decent to me, can play left-back too (not sure about LWB), could be worth a shout.
First choice RWB: I'd keep Baldock as back-up/rotation and move Freeman on, probably. Matt Lowton was suggested by a couple of others, and I think he'd be perfect. He likes to attack, is home-grown, has good PL experience, has fallen out of favour at Burnley so might be available - would be a cracking signing, I reckon.
Back-up LWB: again, I'm not sure who to suggest, but I'm not sure Marvin Johnson would cut it in the PL... Maybe Rico Henry? He's young, looks to have a lot of potential, would suit our system well I think - and we've had good fortune with Brentford defenders in the past!
Back-up/rotational CM: I have a feeling we'll keep one of Coutts/Lundstram and let the other go - so we'd either be looking at a deep lying playmaker or a box-to-box midfielder. For the former, Ryan Woods or John Swift would be great - for the latter, honestly, I think Adam Reach would be perfect, could cover LWB too (and our recent ex-Pig signings have mostly done really well). However, I reckon we'd keep Lunny and release Couttsy (sadly), so I'll say John Swift would be our big midfield signing.
Rotational CAM: Duffy's great, but not getting any younger, so we need an alternative here. Dowell (loan) would be a decent option, but if we were to buy someone permanently, I'd like to see us get Luke Freeman - he seems to have a similar playing style to Duffy, so could be his perfect long-term replacement.
2 * first-choice/rotational CFs: perhaps an unpopular choice, but I'd look to sign Gary Madine permanently - I'd hope to see us use him more as a bench option than a starter, but sometimes it would definitely be helpful to have a target-man and play more directly, given the quality of some of the PL teams in possession. The other striker would need to be someone more dynamic: Bowen, Maupay and Robinson would all be exciting options, but I'd like to see us resign Che Adams - pacy, powerful, and probably still got a lot of room to improve; he wouldn't be cheap, but the sell-on clause could perhaps help us afford him.
So (I might have gone slightly overboard) 8 or 9 new signings (a couple of them on loan), but only 4 or 5 new starters - team chemistry, togetherness and familiarity with our system are some of our strong points, so I don't think there should be too much upheaval. Just need to add a bit of extra quality, leaving our squad looking something like this:
GK: Henderson, Moore
RCB: R.James, Basham, Cranie
CB: Egan, Stearman
LCB: O'Connell, Le Marchand
RWB: Lowton, Baldock
LWB: Stevens, R.Henry
RCM: Norwood, Swift
LCM: Fleck, Lundstram
CAM: Freeman, Duffy
RCF: McGoldrick, Madine
LCF: Adams, Sharp