Slitherine

So I'm halfway through playing as Rome right now. I've upgraded my infantry to Imperial Legions and Auxilia. I've got a front line made up of said legions and auxilia with some cavalry on the flanks. Or least, that's how I intended it to work, but the game puts the legions in the middle, then the cavalry, and then the auxilia, and then the flanks are left bare, because they're reserved for cavalry. So then I get flanked and take unnecessary casualties. This happens with both heavy and medium cavalry, although light cavalry work as I was hoping. I don't remember having this issue with the previous level of medium infantry. This is quite exasperating (especially after I spent like an hour rebuilding and rearranging all my armies). Is this WAD? Is there anything I can do about this? (Aside from replacing all my other cavalry with light cavalry.)

If the front is 16 wide, the 6 outer can only be filled by cavalry as you said BUT it requires you to first fill the middle 10 with infantry. So in this case you need 6 cavalry, 10 infantry and 16 auxiliary + reserves for multi round combat.

Auxilia are infantry though. The title on their unit card is "Infantry" and they use the standard medium infantry description.

Oops confused with the skirmishers ...

Scobie, auxilia replace the Velites. Both have a ranged attack of 5, so they should line up for the melee phase in the second rank as skirmishers. Do you have a screenshot of the battle to clarify what you are describing?

Auxilia also replace the Alae, is the thing. I was expecting to be able to use them in the same way. I see their distance to centre is lower than the cavalry's, but I'm assuming that's overridden by them being set as support.

In the Dbase they have a line that they upgrade from Velites. So they are being treated as skirmishers and you might want to do what Surt advised.

I see. That's somewhat frustrating, both because the game doesn't make that clear and because it leaves me without a viable cheaper alternative to the legions. (If I want to fill out the line while saving on metal, say.) If the auxilia just went inside the cavalry on the front line they could ably fill both roles.

Is there still Italian/Latin foot available at later stages? in that case you could use those.

Light cavalry are better skirmishers and much cheaper to build and maintain than auxilia. They add their flanking value to pursuit attacks at the end of combat, too. So that would be one savings.

Having looked at my military situation I've found some decent alternatives. Thanks for your help, everyone.

What did you chose in the end?

I built more legions and supplemented them with a mix of provisionals and mercs. I've kept the auxilia around to act as second row troops in future armies.