but kensai->blade kinda works using shadowkeeper...
the bonuses to thac0 and ac and damage are all lines in the affects field of shadowkeeper, so you would keep the ac bonus, to hit, damage and kai abilites...
simply make a kensai, then change class to bard, kit blade when you "dual class" using shadowkeeper...you should also roll level to 0 to make sure you don't run into certain problems...
but yeah, using shadowkeeper (cheating) it can be done...