Slugga Boyz, Killa Kans, SAG
I like your style man.
IMO Sluggas should be taken in
big mobs, and bosspoles are definitely no substitute for numbers. You can put Big Shootas on Nobs - definitely do this in the Shoota Mob, and its worth getting one for each Slugga Mob. The Nobs, being characters, then get precision strikes and can allocate 50% of their hits (the 6s) onto any model they like.
PK Nobs though, I reckon they're overrated. Definitely overrated on the shoota mob if not the Sluggas.
You should also definitely consider a
KFF to keep your boys alive on the way to the fight, or if not that, a screen of Grots to eat bullets for you (unless of course, your already using the Kans for that). Since your running 20-mobs anyway, consider allying in Codex: Dread Mob to get a Painboss (
IC Painboy, same cost and stats, can attach him to your boys). Just change the name of one 20-Boys Mob to "Spanna Boys" and remove all their gear and Nob leader, to get the required allied troop choice.
Boys with
KFF/cover and
FNP... man, thats some seriously tough stuff.
Or of course, theres always double or even triple
SAG (with Dread Mob) if your that way inclined