Things could get interesting if Mason scores around twenty five+ this season and we seriously have to entertain that 'Haaland-would-just-block-Greenwood's-development' thing.
6 with Haaland is it not? Him, Rashford, Sancho, Greenwood, Pogba, Bruno. Then there's Amad we've invested heavily in.
It's not just the numbers either. Everyone talks about rotation but clubs don't really change the front four that much. Certainly not enough to keep happy players of this profile want to play every week.
To get Haaland you'd have to make some big decisions on one or two of the existing players.
Greenwood then a confirmed right sided player? Which means Sancho goes where?
4-4-2 (4-1-3-2)
-----------------------Back four----------------------
------------------Proverbial CDM------------------
-------------------------Bruno--------------------------
Sancho Greenwood Haaland Rashford
The midfield would get overrun but on the other hand it would only happen once or twice per match because the entire other team would be under strict orders not to set foot out of their own box.
On a more serious note, you can get six players around 3800 minutes in a sixty game season across four positions, (providing you go deep in all the cups).
Say realistically around 3500 minutes per player, the equivalent of around forty starts. SAF seems to have tried to give them around that. Regarding rotation, 'member when SAF would put out "those lineups" that made everyone scream and holler and rend their garments.
Rooney, for example, had like around 3000-3500 minutes most seasons, even though it feels like he started every single match. (Probably would have been 3500-4000 without the injuries, of course.)
The problem would be Bruno "playing every match" meaning five players for three positions (or six if you count Martial and seven if you count Amad, as you pointed out). If Ole and the staff can handle the minute-planning so that Pogba gets some of Bruno's minutes (and the latter gets some freakin' rest every now and then) it's not un-doable, I think.