I dont often do CO Bus nowdays, (due to etc comping it to crap).
But if Id do, Id prob use something like Adam Daly did.
Which is OB+CO+GW+Armour of Destiny+Other Tricksters Shard and OB+CO+GW+Piranha Blade+Dawnstone+Charmed Shield+Light armour
Tetto eko
Skink lvl 2 + Dispel Scroll
Core of skinks including 2 skink cohort bunkers
Cold Ones/FC a good amount.
Two Terradons to Chaff up Chaff and other stuff that intervenes with the Bus
Perhaps Sallies as well
Nowdays we are facing more and more insane hard to kill lords, and I think the OBs need a tad more defence that the previous list.
My go to builds so far have been:
OB+CO+GW+Armour of destiny+Dawnstone+Other tricksters shard
and OB+CO+GW+Steg helm+Talisman of preservation
the first OB here is tough as a m#"%&ker. Double armour save and 4+ ward is hard to bypass. This guy has Bloodthirsters, Greater Daemons, an Orc lord, a Doombull, a Hellpit etc under its belt. The second OB here isnt as tough, but T6 is nice too.
The problem here is that you need to keep your OB's separated, 1 guy in between for example, otherwise your own OTS will bite you.
Depending on matchup, you could take several other ScarVets with you, for example various CO+GW+1up armour,5+ward save builds.
With Scarvets you can take BSB as well. If ur are facing Regen, take the Eternal Flame banner, but remember, theres always the risk of facing anything with a 2+ flame ward. You can always pop the BSB out of the unit though, if you are not in combat. Magic weapons (which dont get the fire attacks since they are magic weapons), dont mix with saurus characters too well, the +2str GW is just so.. cheap and efficient.
You could take a defensive BSB as well, ironcurse icon + obsidian lodestone.
Ofcourse you need tetto+lvl skink with scroll + 2 terradons + skink core. And the idea is to chaff lots of stuff with the bus handles other things with its multiple str 7 attacks. Still beware of Hellebron and other crazily killy blocks.