So I broke down and bought some of the newer plastics that weren't around back when I was building my armies. I got the Gripping Beast Arabs and their Dark Age Warriors, and also the Fireforge Mongol infantry. Seriously good stuff.
The simplest and most immediately useful application is using the Dark Ages minis as peasant rebels. Just give 'em furry hats and even worse weapons.
Next up, also easy but less relevant to my immediate projects, azaps made from medieval Arabs. Muskets taken from both Warlord's storming party and Perry zouaves, because they're a ramshackle bunch. More variety on the command, ask if you have questions about specific bitz. Even though I don't have plans for an ottoman army any time soon, these guys may come in handy for skirmish stuff.
Finally, two moderately difficult conversions. A szlachcic (singular of szlachta) and a strelets (singular of streltsy). The first is for skirmish gaming (or possibly a dismounted cavalry storming party), and the second is the first of an intended unit. Both are a bit involved, primarily because of the fiddly embroidery on their chests.