There aren't enough active roster spots during the regular season to let the first string offense play a quarter or a half and then rest them. You run out of players pretty quick. Let's try an exercise:
Assuming these Inactives (7)
Slay
Pickett (rib)
CJGJ
Sweat
Book (QB3)
Shipley (for example)
Dean (recovering from injury)
First team players resting later in game:
Hurts
Barkley
Mailata
Dickerson
Jurgens
Becton
L.Johnson
AJ
Davonta
Goedert
Available offensive players:
Driscoll
Keegan
Gates
Steen
F.Johnson
Kinnard
McKee
Gainwell
Davis-Price (elevated)
Calcaterra
Jenkins
Uzomah (injured-abdomen)
Dotson
A.Smith
Wilson
Blasinggame (elevated)
Specialists
Eliot
Mann
Lovato
That's 29 active players, leaving 17 defensive players to play the whole game. And you can't put any of them on the inactive list, it's full.
Maddox
Ricks
Mitchell (who you might not want to play)
Ringo
Rodgers
DeJean
Huff
N.Smith
Hunt
Booker
Carter (who you might not want to play)
Davis (who is dinged up and you might want to rest)
Ojomo
Williams
Baun
Burks
Trotter
Blankenship
S.Brown (who might be suspended)
McCollum
That's an active roster of 49, three over the limit. You have to get rid of three of those guys (cut them, there is no room on the inactive list), and you don't even have enough flexibility to rotate on the D-line after doing that. I just don't know how you manage the roster if you have 8 or 9 guys on "half-game rest." If anyone gets hurt on defense you are going to run out of players. If anyone gets hurt on offense starters will have to re-enter. And who are you going to cut? One of the back-up O-lineman will have to be cut, probably a tight end, and ???.
I just don't understand how you keep the entire first string offense active and then rest them and still have enough guys to play special teams and account for inevitable sprained ankles, twisted knees, and other short-term absences for rest or soft tissue injuries.