Uhm, i was thinking to start someday a campaign in DL, but i hadn't any material ready to do so. Anyway, if u refer to the knightly orders of the first generations of heroes, i would say that
Crown Knight will be the replacement of the paladin core class (without the magic mount, perhaps open even to neutral good),
Sword Knight will be a 10 level PRC (a bunch of level as crown knight as prereq + the standard requirement of 2e to join the order), and Rose Knight a 5 level PRC, having some level in precedents order as prereq, and again follow the requirements in 2e to join the order).
The problem is, in 2e Crown Knight didn't cast, and Sword Knights prayed for "miracles" (my personal way to address divine spells) each week. That could not be so easy in 3e way of thinkin...
Perhaps, banning spells at Crown Knight (more feats than a paladin, no spells, but can turn undead and lay on hands), anf givin' a good progression for Sword Knight and a +1 of casting level for Rose knight could be balanced. I hope that this brainstormin could help.
Steven McRownt