It won’t happen because the likes of Giroud are already unhappy about the lack of playing time. Under your proposals Giroud would have had 0 stars and even fewer mins off the bench this season.
Also even with seven subs senior players are left out of the squad entirely, you think we’re going to leave more out to give a 3rd choice striker some mins if we’re winning?
It’s not going to happen.
If you want to be really cautious you can keep Giroud/Welbeck and loan out Nketiah so he gets more experience, but eventually you’re going to have to make a call and either trust him or ditch him.