I'm an engineer an I didn't know you could use two accounts for different tasks on the same device. Just never thought about it, because why would I? Not a reasonable workaround, I agree.
Anyone with family members using their iTunes account would and has for many years. That's why it's there.
"It's pretty crazy that you need to use the same credentials to "buy" a $0 app as you have to remotely lock and wipe your iphone and mac."
I'm having no trouble remembering the context. Why are you?