Iron Priest on a Thunderwolf (WIP)

It's been a while since I've made a Work In Progress post, and now is as good a time as any. Though it does make sense from a lore standpoint, I wish Rune Priests and Wolf Priests weren't excluded from riding Thunderwolves. That only leaves three different non-named characters capable of doing so, and since Wolf Guard Battle Leader and Wolf Lord are very similar in most respects, Iron Priest is where I get to use my creativity.

The headless and armless horse... wolf-man look is obviously going to change. I've been thinking about Mk.III arms, for the extra protected look, and custom-sculpting a head with some bionic augmentations to it, just enough to mark the Iron Priest for who he is.
I thought it would make sense that an Iron Priest would combine the proven effectiveness of the ancient Mk.IV Maximus armour and the newer innovations, such as the raised gorget in Mk.VIII Errant armour. After all, Iron Priests wear 2+ armour, and this has to be represented on the model.
I have studied historical horse armour for tips on how to armour the Thunderwolf, but horses have typically been protected by quilted cloth and/or chainmail, which would not really work in the 40k setting. Admittedly, GW's own Thunderwolf models haven't been armoured at all, despite having 3+ armour save, so I'm not taking too much pressure from this.

I have no idea when this will be finished. Hopefully relatively soon, but that may still mean months ahead.