They'll never make it Grav only, the standard one is too iconic in a similar way to terminators. I could see a grav variant at some point in the future in 40k or 30k though, there were some grav versions in 30k although they were rare.
I would expect in to be a bit bigger yeah.
They should do loads of weapon options for it, probably across a couple of boxes, to cover standard, crusader, redeemer, helios and excelsior.