I run using the -ian switch so that I can give the AI factions an occasional helping hand: deleting obsolete or severely depleted & untrainable units; re-training for upgrades and replacements; guiding the building queues down more logical and useful paths; and - especially for the Danes! - invading neighboring rebel or enemy provinces that are just sitting targets.

On the latter point, I never start a war, so if there aren't any available rebel provinces the faction may still stall even with my help. For the Danes, I find simply taking Sweden tends to kickstart them into expanding, with Norway swiftly following then either invading across the Baltic or down through Saxony.

Another useful method is to simply give the factions more starting money. This greatly improves their ability to challenge you, especially if you leave your chosen faction's money as per standard, and you don't have to interfear much or otherwise potentially unbalance the game.

As for the refill ability of the King's bodyguard, that is hardcoded and linked purely to the King. Another idea to do roughly what you suggest is to increase the build cost for the RK until it's prohibitively high while keeping the support cost low so as not to bankrupt factions like the Danes and Aragonese. This way you can still re-train the RK for prince/ex-prince units, but the AI will tend not build them.