How about the PvE buffs stack globally? For example, if Chillrend and Thornblade has home keeps for AD, they get both bonuses. Once you enter a campaign, however, the buffs are only dependent on the campaign you are currently in. No home campaigns, everyone in an alliance gets their buffs from the entirety of PvP.

There are currently 5 campaigns, so multiply everything by 5. Keep in mind that this is the reward for taking everything. It is a very unrealistic goal, and you might consider it a one-day event if/when it happens.
Home Keep Bonus: Exp/Gold +25%.
Enemy Keep Bonus: Exp/Gold/Criticals +45%.
Attack scroll bonuses: Damage +25% (or 50%? not sure).
Defense scroll bonuses: Resistances +25% (or 50%?).
Emperor stack: +25 Health per character level (+1250 at level 50).

The scroll bonuses seem a bit overkill, but the rest seems fine.
Of course, we can nerf scroll bonuses by half if this gets implemented (+2% at one scroll, +3% for second scroll).

Comment your thoughts, and feel free to suggest some tweaks if you think there's potential, but disagree with the idea at the moment.