It'd be neat if crusaders with every rune slot filled by a rune got some form of buff. Maybe each effect gets buffed by an amount relative to the average rune level they have equipped, or just a solid x% increase, or a completely separate, unique buff. The graphic on the soul screen shows the body parts lighting up as runes are equipped, finally having the whole body glow and complete the ring around them. I'd like that to represent some 6th buff. Currently, there is no real incentive to put more than 3 runes on ay crusader. Benched crusaders only need 1 or 2 rune types, and most active crusaders only need gold/DPS buffs. Adding a completion bonus would make it more worth completely decking out crusaders with runes they otherwise wouldn't have any need for.