I think it should be done at a clan-level, so that way clan leaders can dictate which craftable items get the bonuses, and then everyone in the clan can choose from that. It would also allow generals to remain in the field, rather than playing hot-potato with troops and equipment.
Or why not just make a separate xp system for strategus? You could specialize in crafting, choosing to make things cheap or make quality. Heir loomed equipment would be more rare and valuable. (As it currently stands, most people don't even bother to make anything less than masterwork items since they cost the same.) You could also choose to be a peaceful trader, which could increase the number of crafted goods you get and a base % of faraway bonus. This would make it more profitable for neutral traders as they could craft more for less in towns their faction doesn't own.
You would gain Strategus xp by participating in strategus battles, this way large clans get hindered by forcing more of their battle XP to be spread out over more people. Splitting a large faction into smaller ones would not help to mitigate this, though they may try having armies attack each other, you could prevent this by disabling xp when a faction attacks itself. This would also reward active players, though you could make it so people from factions other than the attacker/defender get a reduced benefit, being mercenaries after all their services should be bought with gold, not xp.
More war-like players could choose to be generals, with focuses on defense, offense, and speed.
Defense would be things like, being able to recruit more soldiers at a time, decreasing the amount of upkeep you have to pay when the soldiers are in a fief owned by you, or extracting crpg gold/xp from the local population.
Offense could be a reduction of upkeep on soldiers currently in your army, or it could increase the limit before the cost goes up. For example, you could have 60 soldiers for free instead of 49. It could also give you more looted equipment at the end of the battle or when raiding. You could also give bonuses to your army, like +1 powerstrike, powerdraw or whatever.
Speed would be most appealing to traders and raiders, increasing the amount of weight your soldiers could carry, improving the base speeds or reducing exhaustion, and reducing their visibility. A skillful general could hide his army for a speed reduction, the more skill, the more troops he could hide.
Specializing down any one path would obviously make taking others more difficult, master of one or mediocre at all.
Ultimately I think this would favor more war, as peaceful factions would get little Strategus XP, and quickly find themselves outproduced, and outmatched by smaller factions and those that choose to fight.
None of this would have to affect crpg xp which would allow people who simply enjoy the more organized fights and different style strategus brings to continue ignoring the strategus map.
