If you'll forgive me the Texas-style analysis, our central midfield options fall into three categories, and in McGlynn's preferred formation, you really need to be picking one of each to form your midfield triangle.
"Number 6s"/Destructive: Ross Matthews, Frankie Musonda, Blaise Riley-Snow
"Number 8s"/Creative: Brad Spencer, Dylan Tait, Aaron Arnott (?)
"Number 10s"/Attacking: Lewis Vaughan, Ethan Ross, Aidan Connolly
Now that's overly simplistic. You can be a creative number 6 or an attacking number 8, but those are the broadstroke typesets we're working with. McGlynn has also proven during Matthews absence that you don't have to have one of each (although throughout that period I'd argue we looked light in the middle).
I've listed them in order of preference there, and it highlights a couple of issues; we have an over-reliance on Matthews, although Musonda could fill that gap, and that without Spencer for months and Tait going, we're incredibly fragile when it comes to midfielders who can link the defence and the attack. That's not news to anyone, and it's quite clearly the biggest priority for January.
On the other hand, Ethan Ross is about as good a replacement for Lewis Vaughan as you could possibly expect, so once again, a tip of the hat to McGlynn and the board got getting that deal done.