Possible project for next year, what would you recommend for 1860 redshirts? I thought of ACW kepi/sack coat figures but all other suggestions welcome, given the variety of headgear worn 

Another option might be RSI03 - Bersaglieri - Skirmish.

I think some redshirts wore felt hats so maybe Western theatre Union infantry or Confederate infantry depicting shirts tucked in.

At 6mm, you can field the redshirts with the ACW figures in kepis and hats (sack coats and shell jackets) along with the bersaglieri. 

You can probably cobble together a Neapolitan army using the Piedmontese. Same for the Papal forces athough there isn't a good proxy for the Pontifical Zouaves. The ACW and FPW zouaves look like they are both in fez as opposed to kepi.