It's possible to get 7mm dice and little frames to hold them at the back of a base.

I'm planning on using them (on artificially deep bases) for my ancients and dark age units.

Think about "Impetus style" bases and you'll see that the dice can be fairly inoffensive.

Bit late to the party with this response but hopefully better late than never!

I use Pendraken 5mm dice holders (little squares of mdf) and 5mm dice for my home-grown Sumerian City State rules, as shown below.

Don't have any of the Baccus figures for this period based or painted so the figures below are Rapier Miniatures

Yep - we use either 5mm or 6mm dice either in a frame at the back of the base - or a seperate casualty figure with dice cage.