Add BI Consumer role to "View Deliver Full UX" then they will be able to see the Subscribe option. Looks like you have wide open on creating agents (screenshot shows set to authenticated users) restrict this to specific roles (may be only BI Author Role).

Though you are thinking only BI Author Role can create agent, it is not so. If someone access direct agent url ( yourserver/analytics/saw.dll?IBotSummary) then they will be able to create agent with your current setup until unless your restrict 'Create Agents' priv.

Here is agent access levels most restricted to full access.

a) Access to Delivers

b) View Delivers Lite UX  (able to view but they will not be able to do anything)

c) View Delivers Full UX  users will be able to customize /subscribe unsubscribe.

d) Create Agents: something with this priv he will be able to create agents.

e) Modify Current Subscriptions for Agents : With this some one else can modify existing subscription (deleting users from subscription , add )

I hope this helps you !