DESERTOPA'S PROFILE

Time travel is super complicated to do in a coherent way. Chrono Trigger does an okay job storywise because despite using it all the time, the characters barely discuss its capabilities and limitations, and even if it doesn't actually work consistently, the player isn't encouraged to examine it closely. Ironically, using time travel less will probably tend to result in making it even more obtrusive, because players won't be able to help asking "why don't they use time travel in any of the other situations it could hypothetically have resolved?" To make it work, you pretty much have to turn it into a game mechanic which players just take for granted, or devote an immense amount of effort to making sense of the whole thing.

Unless you're okay with flagrant Timey Wimey Ball continuities, which personally I am not.

It might be best if you don't consider yourself too beholden to real life events. When I have trouble coming up with ideas within a certain scenario, I often find it helpful to look at the circumstances I've set up, and ask "What's the most obvious consequence of these circumstances?" If the situation itself is interesting, interesting consequences should follow naturally from it without your needing to force them.

If you want historical bases for your ideas though, for the setting with the good king and corrupt nobility, you might want to try drawing on the French Revolution. Louis the XVIth was a relatively progressive king who tried to reform France according to the ideals of the Enlightenment, who was opposed by his country's nobility. When he supported the rebellion of the American colonies against Britain, he also racked up a debt that seriously destabilized the economy of France, leading to increasing dissatisfaction with his regime. Despite his progressive intentions, he ends up villified a symbol of the old regime and gets beheaded by his own people.

As for the country which values power to the point of allowing anyone a position of leadership if they defeat one of the current leaders in a duel, consider just how unstable a form of government this is. Changes in leadership are probably more rapid than its ability to implement most of the directions from the leadership, and the leaders are selected by a process that has nothing to do with skill in statesmanship or command. There are a few ways this could plausibly play out. First, the country might undergo a regime change which replaces the council with a more stable form of government (here's another place where you can draw on the French Revolution, or rather the Reign of Terror where France was ruled by a revolutionary council with extremely high turnover, which also imposed high turnover on the municipal and military leadership via execution, which lasted about seven years before Napoleon performed a coup d'etat.) Second, the country might fracture into multiple self governing states which administrate their own needs due to the ineffectiveness of the central government. Third, the country might be toppled by neighboring states which capitalize on the present instability to move in and take over.

Okay, I didn't understand from your first post that the system in your new game would only apply to monsters. That definitely limits how much impact you'd want to give it on party construction, but making the items only usable by or on monsters does sound like it could be a viable solution.

If there's literally no incentive to unequip souls, I wouldn't bother with it, but I think it should be possible to offer interesting incentives for doing so. You said that replacing one soul with another destroys the old one, so maybe unequipping them doesn't. If you can keep souls which you've acquired and then removed with the soul render, then you should be able to find something interesting to do with them. Maybe rended souls become consumable items, or can be traded in for some sort of goods or services, or both. You might tempt the player with mutually exclusive bonuses, where one might acquire souls from a unique monster, and choose between some valuable use, or trading them in for some other valuable thing, one a one-time-only basis.

Unless there's a strict progression whereby the souls the new souls always offer better bonuses than the ones available before them, I think you might want to consider giving the player some way to store souls that have already been obtained and reequip them, if not at any time, then by visiting the same NPC who allows you to unequip them, otherwise players may end up doing a lot of annoying backtracking to reacquire souls of monsters that aren't available in the current area for the stat bonuses after taking on new ones for the moves.

How much incentive do the players actually have to unequip souls at any point, rather than simply absorbing new ones as they encounter them?