I would like to see having to manage position player stamina/energy.. as far as Ranked Seasons, not really for BR/Events.
Wouldn't even make a drastic difference, with an example being in Franchise mode you can play 5, 6, 7 games straight before really having to make a move to your bench.
Obviously factor in particular postion for percentages (1B loses much less energy than C)
With 5 bench spots it would add a bit more strategy besides punch running & hitting & you'd still be able to pinch hit your resting players.
With so many solid players in the game it would add an interesting dynamic, plus a way to test the depth of your squad