hmm.
while the overall theme is pretty cool and interesting, there are a couple of things wrong with it.
the emperor himself never claimed godhood, and never renounced his own humanity or demanded worship.
now as they learned this from the black legion, is this belief taken from the corrupted truth that the chaos legion told them? that would make sense to me, but its unclear.
but are they fighting the imperium or chaos?
IMHO they should actually be fighting chaos, but be independant of the imperium. even with their corrupted view of the emperor, i dont think they would so swiftly denounce the imperium and join chaos. after all, they were the ones lorgar marked as feirce loyalists. just my 2 cents on that
for modeling and painting, you could do a pre-heresy word bearers scheme, or a different color scheme since they were betrayed and no doubt dont want to be associated with the traitor legion.