I kinda like the suggestion for bandits wearing the familiar Robin Hood style costumes, even if it might be more appropriate as a "Classic Fantasy" set or possibly niche enough for only a Digital release.
I'll add another tap on the old drum for a robed monks-and-cultists box. I think I saw someone somewhere try to argue it would be too hard to do, but after souping up a quick band of post-apocalytpic mutants using Oathmark Goblin Slave bodies with Wargames Atlantic WWI/WWII Russian bits, I'm convinced that it shouldn't be THAT hard to do: those goblin bodies are pretty close to what I would picure for a set like this, needing only longer robes, I think, and the arms/sleeves wouldn't be much different from what WA has already done with the Boxers and Afghans, and hooded heads are just about ubiquitous in hard plastic sets for Oathmark, Frostgrave, and Stargrave and should be easy to do.
Sure, the monks-and-cultists thing might be another set more appropriate for fantasy, but either way it's something I'd make use of.
I'd add at least moral support non-Western European sets in digital or plastic for "Age of Chivalry", Renaissance, Dark Ages, or anything in between or beyond - that Mali and African idea is intriguing, and I love the box of "Steppe Warrior" mongols I picked up from somewhere a few weeks ago, and would definitely buy them by the box from Wargames Atlantic. East asian, middle-eastern, Eastern European - all seem like fascinating subjects, even if they're niche compared to the Western European thing (which will surely be at least as popular for fantasy gamers as for historical gamers!)
I've never gotten into 3D printing, but I've really been enjoying the "What If?" Digital subjects, like Dark Ages Native Americans and so on. Again, even if it's more suitable for Classic Fantasy, I'd get a kick outof "What If?" sets themed around Age of Chivalry. Elves, dwarves, halflings, and the like in Knightly armor? Sounds like fun! What if neanderthals / Hollow Earth "Cave Men" had survived into the Age of Chivalry, what might these wild men look like, use as weapons, wear as armor? What if the Age of Chivalry had included extinct megafauna monsters? I like the handgunner idea, even if it is perhaps anachronistic - what if?
Digital seems like a great way to release quick-and-easy kits for simple subjects like crowned kings and lords, along with retinues of court characters like messengers and scribes, musicians with drums and horns/trumpets and bells, priests and bishops, jesters, and so on. "What, on a medieval battlefield, are you crazy?" Yes, and yes - these characters would be fun for fantasy gaming, and maybe they work quite well on the organized battlefields of medieval tournaments. I'd buy a set of such characters by the box in customizable hard plastic if I could.
Honestly though, it otherwise seems like the Age of Chivalry is pretty well-covered by the Knights, Seargeants, peasant Levy, and mounted cavalry sets. Those four sets cover a ton of medieval territory quite nicely!