Besides being cool looking, they are brutal on the battle field. I've no plan of running them with flesh-mowers or greater blight launchers. The plague spitter in combination with the FLY rule is a bloody combo. A must in a Death Guard army.
I've been very succesful with keeping a Herald of Nurgle nearby, buffing the strength of their weapons and healing them if injured.
I haven't done any conversion work on these models. But I have used different colours for the skin, boils and metals. And added some different stripe patterns on the front of them as well.
I have three more of these models, but I'm gonna convert them into Mythic Blighthaulers instead. Get a bunch of cool bits from them as well.