I've found a way to enable 3rd party apps without going into security settings (like if most of could anyways

). I've tried it on a a few apps and Aptoide is the only one that failed for me, hopefully it was just the apk.
I was rooted using SuperR's 4.1.2 rom (based off of KK), flashed the partition fix, then the deodexed rom, then the sd card fix. Just thought i'd throw that out there. You WILL need to be rooted!
Go into the Play Store and search for "Secure Settings" should be a gear icon, install and click the "SYSTEM+" tab and enable it, after that go into the options tab and then click "System+ Actions" and make sure "unknown sources" has a green check. Once completed head to the widget section in the app drawer and look for "Secure Settings" once more, select the "System+" drop down and click on "Unknown Sources" it will then ask if you want the widget to be a 'on', 'off', or 'toggle'. Click toggle then the click the save icon above twice (there will be two pages, second will be to customize appearance and name). After the widget has been made click it and test it out on a couple apks you trust, if it doesn't work reboot and click again.
I am not 100% sure if this will work on your device since I own only one and things may differ from yours, if this does work for you please say so. Now if only I could uninstall all of these other apps I downloaded while I was searching