The AI needs (nearly) correct numbers of each troop type to do so. So, it cannot form a manipular formation with 5 Lugoae, 1 Extraordianrii and 2 Triarii.


Quote Originally Posted by QuintusSertorius
I don't use any of the default formations, because they're no good for the Roman quincunx. It does get a little annoying having to carefully re-order my troops at the start of every single battle, but what's worse is when I sometimes try to move them all, and it tries to re-order them into a single line.
Deploy your units, select all, group them, ungroup them and group them again. That should do. (Even though I find it eayser to just group the infantry block and move the cavalry seperatly)

Is it even remotely possible to delete or otherwise negate the formations that are there for the player?
Check the unoffical modding forum for battlefield formation mods. These files are also moddable.