So, Warmaster Horus and I have worked out some basic ideas as for how to play. Really, it's all a simplified version of the KotR way of playing. Of course, these are just suggestions and everyone is free to come up with suggestions and alterations:

First, we have the Chancellor. A player who works as the "mod" and who does all the dirty work. The Chancellor will be the one who constructs buildings and recruit troops according to other player's suggestions (see below). The Chancellor also moves troops around. If there is a battle, the Chancellor will send the game (via e-mail, for example) to the player who's character or province is involved (see below) who then plays the battle. The game is then "returned" to the Chancellor who continues as above.
The Chancellor has some power however, and can be a provincial ruler (most likely the capital or whatever big city that is closest to the King's position, for more info see below). The Chancellor can also engineer domestic troubles if he wishes to; i.e. by spending a little extra on himself and his own province, which should likely provoke some disputes. The Chancellor can also engineer civil wars (this is done in-game) by being convinced (perhaps by bribery) by some prince or such to assassinate the King.

Then there is the King (or Doge, or whatever). The King is played by another player. The King is the one who makes all the final suggestions, but not without the influence of other players (see below). A King must be roleplayed (i.e. if the King has the vice "irritable", he will not be keen to settle with truces and such, and a king who is known for executing prisoners must continue to do so, even it earns him some nasty vices). More than just having the final word in financial matters and politics, the King is also responsible for the main army of the kingdom, and must command all larger, offensive, campaigns. Good commander or not.
When the King dies, he will be succeeded, so players who chose to play as the crown prince must consider that they will likely end up as Kings.

Then comes Princes or Heroes (as Heroes, all scripted heroes and random generals that spawn with 4+ command (unusual, but it happens) counts). Again, these must be roleplayed as above.
There is however a difference between Princes and Heroes. Princes can't be landowners, and are solely for military purposes. A Hero is more stationary, and if he is granted a provincial title by the King, he must remain in that province untill stripped of office.

Finally comes provincial rulers. These are not "seen" unless a provincial title is handed out. That is: I can play as Tuscany withouth there being an elected Duke of Tuscany, but if there is a hero who earns the title, these two will be merged into one (unless both players disagree to this of course, in which case the problem most be solved in other ways, like the Hero not earning the title in the first place). A provincial title can not be given to some random general with high acumen, only if he is a noble (i.e. a Hero, see above).

And finally a little bit about warfare: For the realism of it, we should keep our armies balanced, quite simply. A core of elite troops surrounded by lesser soldiers.
A good rule is two units of retainers (like Mounted Sergeants) per one unit of knights. This means: If a provincial ruler wishes to recruit one unit of knights in his province, he is forced to recruit twice as many retainers, as these provide the servants, squires and well...retainers for the knights. Of course, as the eras pass by, previous peak units will be conisidered as retainers (so we could use Feudal Knights as retainers in High).