BM with all due respect sir, escape routes are not ment to "optimise" they are exactly what the name implies, an escape path from high terrain in the event of a decompression and a diversion route to an en-route alternate. As you correctly mentioned airlines have them in areas of high terrain to give crews the ability to both descend as well as stay safe from high terrain while diverting.
For example close to Tehran in Iran there are escape routes from the airway to divert to THR airport while avoiding high terrain.
Again as you correctly mentioned they are designed for decompression problems and not so much engine out situations as most commercial aircraft be it twins or four engine aircraft do have the ability even with one engine out to stay above MSA's or Grid MORA's of even 19000ft.