Well, then increase the area not two, but one and a half times? Okay, then can it be done as a technology for the third phase of the city? Then it won't affect the early rush.
From the outside, it looks as if all nations suffer from early medieval astigmatism and see nothing further than their own nose. Age of Empires 2 has sentinel tech, so why not make it in 0 A.D. the ability to increase the radius of light at least one and a half times by placing a unit in a building? Well, or at least add the visibility radius of the building with the most large visibility radius of the unit inside?