You are right, this is a good reminder for upgrading army.
In games with ceasefire, you get an alert with "you can attack now". Maybe we can create similar alerts. To create an alert with the mod, you would need a field "alert name" e.g.,"p2alert", a field "time" e.g., 9:00, a field "message" e.g.,"phase 2, phase 2, phase 2".
Another possibility is also to create an alert based on your resource vs ally resource. I think this can be based on proGUI. Rather than auto-tribute, you would get an alert (like blinking on the resource amount display) to indicate that you have a lot of the resource and an ally is critically low on it or the inverse.