Tactics wise, I use give these fellows Furious Charge, attach my Marine Master to them and put them into that Land Raider. This squad beelines for the heart of the enemy infantry and lays down the smack. The Apothecary keeps the squad somewhat intact on the way in, while in the rare cases where I dont run the Land Raider and keep the squad back in defensive situations, the banner-bearer gives the core of my army Ld:10 with a reroll. The Death Guard were known for their perseverance!
Modeling wise, these guys are all specialists such as the Apothecary, or are using the earlier marks of armour as befits their veteran status. The banner-bearer is even sporting his Mk2 Crusade Armour, alongside several Mk 4 brethren. The Great Company banner was also designed in Adobe Illustrator and printed out. As members of the Command staff they got the snazzy golden exhaust vents on their backpacks… Pretty Fancy 😉