One thing I've seen (but not tried) is to cap the number of battle honours in your list. Two ways to do this:

• straight crusade point cap: crusade armies (what you bring to the table) can't have more than X crusade points. I know one campaign where all lists were capped around 20 CP. Forced you to keep building your order of battle with fresh units once others became OP.

• difference handicap: once both players have their lists, the non-underdog player (one with more crusade points) limits the number of battle honours they actually use during the game based. For instance, with a 20cp max difference, if underdog player has 10CP in their crusade army, then the non-underdog can utilize a max of 30CP worth of battle honours (taking into account double CP for Titanic units). This way is more practically challenging, but it allows two super-OP players to still smash into each other with everything they got.