I've been working on exactly this, but just for the saxons so far, because just like you I loved having elite troops in shogun 2.
I'm slightly insane and obsessive and I've been fine tuning this unit for like a week straight but I'm pretty pleased with them now, these are my saxon champions
http://imgur.com/a/64Wzb
they're 30 men strong and have absurd stats (like 110 attack 90 defense 300 morale) but actually seem fairly balanced. being only 30 men strong they can't withstand a charge very well but in a simple melee can stand up against one unit of almost anything, but anything more than that and they get overwhelmed and die. they also get completely wrecked by precursor javs (because any jav volley will take like 10-15 men leaving them pretty weakened) so you need to use them very wisely.
however put them in the right spot and they can cause mass routs because of the fear they instill in the enemy, and they're great general assassins.
They use assets from multiple mods on this forum though, mainly weeags shields and hadriens awesome saxon overhaul, so i wouldn't feel comfortable releasing them without permission (which i might ask for down the road.)