For all our issues in midfield, I think if we have to priortize 1 position for a transfer, it should be a forward player, (as we might not be able to afford a CM and a FW)
This would help us pull off a 4 - 2 - 3 - 1 as a back up system maybe for 10/15 games perhaps permanently if it works well enough, this will help in a number of ways.
I suspect there are only 3 CM's that klopp truly trusts in our squad and 4 forwards. A 4-2-3-1 introduces a number 10 and in that position he might be able to entrust keita/shaq/AOC more than currently. Many will say injury is why they don't play more, but Klopp has had matip playing at CB, with gomez and lovren on the bench many times. If a player is good enough Klopp will try them, but I don't think he trusts keita, or AOC defensively, or even jones.
Of course Firmino would the man that could benefit the most from playing as a '10'. He is a better creator than he is a finisher. And considering the season's Firmino and Mane had last time around, and their (and salah's) age it would make sense to have jota plus another youngish forward who klopp trusts. Having Jota, Firmino an and another top forward could be crucial during what has proved to be the toughest months of the season under klopp (jan/feb) when AFCON will be occurring.
Having to pick 2 from hendo, thiago and fab might help extend their careers
Playing 4-2 -3-1 might impact the fb's, but I felt we struggled last yr, from our midfield playing as conservatively as ever AND our Fb's playing as they did. Having a proper no.10 should aid our front 3 better. I feel we have better personnel than we did in 2018 when we tried it last, especially if we bring in another FW