How can access on an android device be restricted to applications or widgets on the home screen only? This is a rooted Nexus 7 with 4.4.4 (factory image from Google).

I'd like to restrict access to anything that's not on one of the home screens. 

Apps and widgets on one the home screens should be the only thing accessible without entering a code. Ideally, just activating the apps button that shows the full list would ask for a code. The link to the full settings page from the drop down menu by the clock should also be locked.

This does not need to offer a high level of security against experts, just a basic level of protection.

Strong preference for open source solutions, but let's see what's available in general. Maybe some kind of a launcher?

Existing kids mode solutions are not a good fit. I didn't look through all of them, but they seem to limit the number of available apps, and would not be suitable for an adult due to their interface.

Kiosk and app lock solutions: I reviewed quite a few options. Some are geared towards showing a web page only, others have odd intentional characteristics such as not starting on boot. Most, however, have a long list of permissions that have nothing to do with their functionality. This is a common problem that open source apps tend not to have, hence my preference for them.

Thanks in advance.
It turned out that there's a solution without using additional apps, at least on 4.4.4.

Settings -> Users -> Add user or profile -> Restricted profile.

From there, it's just like an app locker, where the apps that should be accessible are turned on. Once the restricted profile is active, the apps that are not active are just not visible in the apps list.

The best thing about about this is that it's a built-in solution that doesn't require questionable permissions granted to an app.

Negatives: the main settings app can't be restricted for some reason and the system apps that are supposedly disabled, suddenly become active, which is particularly bad as the description for the feature says that it restricts access to apps from your account, so you'd have to do it all over again.

Advanced: Restrict Me module for Xposed is supposed to enable turning off settings as well. Not tested.