This is the only solution atm and it sucks. It might work with a few trustworthy friends but leave your device open at a party as music station and it's way to convenient for someone to "accidentally" open the email-app and instantly see all your private emails.
All that's needed is an app-lock and you could use this workaround. You make all your private apps password protected and guests can only use the browser.
I would love the option to login as myself and have basically just my account keychain applied to all installed apps. I can't imagine that would really be that hard for Apple or Google to do, and it would really take Tablets to a better spot in the market as they aren't really phones at all.