I've been thinking alot about the "what do we do with Nwaneri discussion" and I think I have a solid option.....
Arteta has tweaked our formation/tactics atleast a little every season since he has been in charge. We've played a 3-4-3, 4-2-3-1, 4-3-3 with traditional FBs, 4-3-3 with 1 inverted FB and now 4-3-3 with kind of hybrid FBs. An idea I had would involve another formation/tactical change. While it may be unlikely that we shift back to a 3-man back line, I think it could be worthwhile to mimic Leverkusen where Xabi Alonso teaches the same types of spacing principals as Arteta but with a different setup.....
------------ Havertz ------------
--- Nwaneri -------- MO -----
MLS - Merino - Rice - Saka
---- Gabi - Saliba - White ---
------------- Raya ---------------
Above is current roster with everyone healthy.
Move to a 3 man back line. All of the defenders that are expected to stay, except MLS are naturally capable CBs and many of them have played in a 3 back setup previously. Gabi, Saliba, White & Cala become your primary rotation. Timber can play on the outside or can be shifted to DM/CM or play as a defensive WB. Tomi (if ever healthy) can play all 3 spots and Kiwior likely still gets sold and is replaced by someone young.
Rice in a double pivot is a much more natural role for him and finding quality players for a double is easier than a single pivot. You can still bring Zubimendi and use he, Rice & Merino as your primary rotation. MLS would be a very strong option for LWB or one of the DM/CM spots. I pulled Saka back to RWB because (a) he is already a strong wide defender and (b) WBs are heavily involved in the offense in this setup with (c) Grimaldo (LWB) being the leader for G+A for Leverkusen last season and both WBs being top 5 both this season and last. Could add Timber to this group as a more defensive option for both sides and would likely need atleast 1 guy added for depth..
For the AMs you have MO & Nwaneri. Could probably play Trossard in that role as well as Havertz if/when a new ST is brought in. Chances are you would need to bring in atleast 1 guy for depth.
The only player that we currently expect to stay that I have a hard time fitting into a role for this formation is Martinelli. While he is decent at tracking back, I don't see him being a legit option at WB. I also don't see him being creative enough for the AM role. Think he would either have to moved to ST or be sold.