I've been kicking around the idea of a Spartan Assault Tank and how best to use it with my army.
Obviously, it would "have" to belong to an allied detachment of CSM. But inside of it, I think I'd put 24 KD Cultists with a Herald of Khorne + Locus of Wrath. Upgrade the tank with a dirge caster, frag assault launchers, and one of the legacies of ruin. Either +1 khorne daemon save within 6", or 12" dirge caster range. On such a big tank, either one will work pretty well. 12" from that hull is a big chunk of the tabletop!
There are obviously deadlier units to put inside of the tank, such as Berzerkers, Terminators, or even a ton of Bloodletters with an Icon to precision DS other daemons of khorne (the only other viable option, IMO). With the +1 save upgrade, this unit would make more sense if anything is deep striking.
But the issue is cost. This is already a 300+ point investment not counting the unit inside. Fearless cultists with Rage rerolling misses in the first round of combat is pretty solid. (24*4)+1 for champ = 97 attacks on the charge ignoring the initiative penalty for charging into cover.
With the cultists, herald, and decked out tank, that's ~560 points. Still a huge chunk of the army, but leaves plenty of points for some friends to play with.
In general I favor MSU style play with KD, but this is just an alternative to that. A relatively cheap tarpit that will survive to cross the table (let's hope). The herald can actually put in some work on the charge, and can sit out the challenge if it makes sense.