Here's what I've come up with so far:

• Rather than the series' usual royal-centric plots, have the player take the role of a peasant revolution to overthrow the country's nobility.
• Go the opposite route of the series' typical Lord protagonists: the main character is a bow-wielding peasant, because they grew up using a bow to hunt. Maybe being sentenced to death for poaching on a noble's land to feed their starving family (but gets rescued by the revolutionaries) is the catalyst that leads them to join the fight.
• The Jeigan (prepromote with high initial stats but poor growths, meant to help the player through the early game) is a Smedley Butler type figure. They're a paladin who rose to prominence in the royal knights but defected to the revolutionary army after they realized that their "heroic quests" mostly came down to butchering innocent people.
• It turns out that you don't need to come from the right bloodline to use the amazing, one-of-a-kind holy weapons. The nobility just made that up to justify hoarding them and to legitimize their rule. Over the course of the game, your peasant army seizes and gets to use some of these weapons.