Right now, every single game of WOM lives in it's own universe and there is no connection whatsoever.
What if one sovereign could progress through say, 10 games in a row, gaining XP and getting a little stronger for it?
Warlords Battlecry had such a system, IIRC.
The technical issues couldn't be so tough. Every game needs a unique identifier, much like the Metaverse games. When you end such a game (even by giving up), you'd get some XP and your sovereign could eventually level up - completely independant from the leveling in a game.
The played game history would have to be saved with the sov to avoid "winning" the same game over and over by reloading the savegame. =P
Maybe a higher persistent level would allow you to pick more advanced traits than the ones you can pick at the start. Or you'd simply get points to buy more traits/stats or buy off disadvantages.
Of course you couldn't unbuy things you bought before. That would defeat the whole purpose of development. =P
Items would also be a possibility. High level quests could rarely give you items that the sovereign could keep permanently. They couldn't be very powerful because it would ruin the whole game to start every new game with a 50 ATK sword.
Instead, their effects should be tied to the in-game level of the sov. Like a sword with (Sov.level / 2 + 3 ) ATK. You can let the player start with a weapon like that...
Such quests could also grant knacks for specific spells. Like +3 % damage with firebolt only.
Things like that would seriously make players reconsider the adventure tech tree...
It would be hard to allow the carryover of a "loyal retainer" unit.
Like... you buy the trait "Retainer" and then you could assign one unit in game to be your personal bodyguard or whatever. They would be able to enter the next new game with you.
The problems start when that just happened to be a company of adamatium plated elite heavy archer cavalry.
Maybe you'd only get the chance to assign such a unit in the first x turns of a game. That would limit what you could have researched / built by then.
Still - it's only a vague "would be cool" idea but I have no solid plan for balancing it.
In principle it would be like one of your "core units" in Fantasy General or comparable games.
It could be a rather generic unit like what the Warlord trait gets you. Only these would keep their XP (or rather some of it) if they survived to the end of the game.
All in all, it would create more incentive to... play games. A lot of players love to compare stats and rankings. That sorta stuff.
I'm more interested in some way to progress. To be able to beat higher difficulty levels that would be murder with a "noob sovereign"... =P
Of course, I could mod and cheat myself any sovereign I damn please but that would be boring. Why would I want to do that?
The whole point is in the development / growing procees so why would I bother asking for it and then completely bypass it?
If and how these "leveled up" sovs would work with WOM multiplayer - I don't know.
Multiplayer is no consideration for me...