I agree that the current WoG Hell Steed/Nightmare looks much better.Nice... I think I liked the other Nightmare better, but great to see some move. Hope that you'll find the strength and time to finish this project.
But it depends what HotA has in mind regarding the creature. If they want to make it an Inferno alternate creature, I guess the new design is fine.
But this reminds me of a question I had for the HotA developers (sorry if it was already asked): what do you have in mind for the current so called "Neutral" Town from WoG? Keep it or scrap it? And if you leave it out, do you distribute the creatures as alternates to the existing alignments, or you leave them as neutrals (thus still leaving an open possibility to reunite them in a town with new graphics at a later date)?