Change is simple enough that it fits into the title. It could be 'highest unlocked Melee unit' instead, but this keeps the policy text shorter.
The other two ancient trees get a free unit in an early-ish policy, so this change would be aesthetically pleasing. Currently the Artist vs Engineer choice at the start of Tradition also is a boring no-brainer and this would spice it up. Even the Flavour works great since the building granting the Engineer is a guardhouse.
I am not a balance expert, but it is unlikely that a single free melee unit will break things in a bothersome ways. AI is swimming in free units anyway and if a player is good enough to incrementally turn a single Warrior into an overpowered advantage they deserve it.
The other two ancient trees get a free unit in an early-ish policy, so this change would be aesthetically pleasing. Currently the Artist vs Engineer choice at the start of Tradition also is a boring no-brainer and this would spice it up. Even the Flavour works great since the building granting the Engineer is a guardhouse.
I am not a balance expert, but it is unlikely that a single free melee unit will break things in a bothersome ways. AI is swimming in free units anyway and if a player is good enough to incrementally turn a single Warrior into an overpowered advantage they deserve it.