I just wanted to post what i came up with as a solution the the problem of not being able to Test the effects of sandbox changes for non admin level users prior to their publication. We are constantly making changes to the UI through sandboxes, the problem is rolling a sandbox back isn't easy, and we cannot be sure of the effects they will have on non administrative users until they are published, since the out of the box sandbox link isn't available to non Sysadmin level users.
To allow these non admin user accounts to test the effects of sandbox changes in our development environment, I did the following (as always, follow at your own risk):
- Create and activate a new sandbox.
- Close all open tabs (including the Home and Sandbox tabs) and click the "Customize" link.
- Click the view -> source drop down in the upper left.
- After the source is visible, click the Accessibility or Sandbox link to find the area that you will add the new "UserSandboxTest" (call it whatever you want) link.
- Add a new commandImageLink directly in the panelGroupLayout: horizontal item before the "switcher" item (see the UserSandboxLink in my screen shot below):

- Edit the Link you just inserted, Entering whatever you want the link to display as in your browser in the "Text" field.
- Export the sandbox.
- Unzip the exported sandbox and navigate to the IdmShellV2.jspx.xml (path should be: \templates\mdssys\cust\site\site).
- Edit the IdmShellV2.jspx.xml file and find the new item you added in step 5.
- Add the following to the commandImageLink xml item: actionListener="#{pageFlowScope.uiShell.context.launchSandboxes}" rendered="#{oimcontext.currentUser.roles['SANDBOX_USER'] != null}". Note: I used a new custom enterprise role, SANDBOX_USER, to control the display of the new link, You should substitute whatever EL conditions you need in the rendered property.
- Save your IdmShellV2.jspx.xml file and zip the contents back up, just like you would for any other customization.
- Import your newly edited sandbox back into the target environment.
- Publish the sandbox.
This seems to work great for allowing us to test other sandbox changes effects on different types of users.