As for whom we should get, I remain convinced a 3-5-2 is the way forward, and for that we are a CM short. I'd take a look at the market for an offensive- minded CM in January - high-ambition target could be someone like Milinkovic-Savic (still at Lazio), lower-ambition target could be a loan-to-buy deal for Weston McKennie from Juve - Juve themselves are struggling and might want to let him go for cash, and he's a mobile, physical, hard-working box-to-box midfielder who I think is being misused at Juve like Benta was.
As for the trouble with letting the likes of Tanganga and Spence go out on loan, it's that we are already at our minimum for HG players in the squad, and that's with both of them + Davies registered as HG players.
Meaning we'll need to replace them with HG players if they leave - difficult in January. Jason Denayer could be an option if we wanted to pick up a relatively cheap player - 27, experienced, good on the ball, was free this summer but ended up signing for a club in Dubai on a short-term deal. Can't imagine he'd cost much, and would be no worse than Tanganga as an RCB backup. HG because of his time at Emirates Marketing Project and Sunderland.
Maddison might be available. Leicester may need to raise funds to strengthen. Not sure if we're interested though.