Is it possible to make 'admin' user apps available on other user accounts?
As far as I know: Not at all.

Each user account is strictly separated from another and there is no shared folder or app sharing concept at the moment.

I haven't checked your specific question in detail, however each user has their strictly separated userdata partition where everything is stored (even their media, on Nexus devices) and cannot access any other's data residing in their userdata section, which includes user installed apps (they're in /data/app/).