If you can convince someone over the phone to install malware thru a million "don't do this" screens, you can convince them to just give you their login credentials. Which is both easier, cheaper, and, I imagine, more effective.
And I'm being extremely generous here, because this won't erradicate malware. It will make a specific subset of malware harder to distribute. I imagine most malware is distributed through the play store, and naturally that will be unaffected.