The questionableness of chonky Deathclaw aside, KF on dragon is somthing that is almost never done. Mostly because there is no real Imperial Dragon model that I am aware of.
I think perhaps they included it in the 7th Ed book for the sake of encouraging people to get in too conversions. However a dragon of the era is a massive project not just to paint but also assemble. Remember that this is before the introduction of resin or plastic beasts/monstrous mounts, all metal.
By the time the plastic and resin dragons did start to appear was pretty much the end of 7th Ed, not to mention that dragons were pretty obsolete by that point...