Quoting: Logan_Ollivier
If you replace Mangiapane and Nelson with Kampf and ZAR you can likely fit McDavid and then this team is the best.
Aston-Reese is not currently signed. Let's say he signs to league minimum and take a look at the numbers.
Kampf: 1.5m, 1.03 WAR, 0.686 WAR/$
ZAR: 750k, -0.23 WAR, N/A WAR/$
Mangiapane: 5.8m, 5.32 WAR, 0.917 WAR/$
Nelson: 6m, 4.34 WAR, 0.723 WAR/$
McDavid: 12.5m, 7.95 WAR, 0.636 WAR/$
Mangiapane and Nelson are a more efficient use of cap space than McDavid. Their 11.8m is worth 9.66 wins, whereas McDavid's 12.5 is only worth 7.95. Kampf is more efficient than McDavid as well, but ZAR would be a detriment to the team. Of course, this is all using Bacon's WAR model, so if you think it's low on McDavid or high on Nelson and Mangiapane, that's totally reasonable.