Hmm, well despite the shape of the front putting it firmly in the category of what my friends and I would call a "clown shoe" car, I think it could be a very workable HQ
vehicle. The distinctive profile and general look speak of excess and frivolous luxury often attributed to the elite in the Imperium. Perhaps the leader of your cult is actually the Planetary Governor or a wealthy noble and this is their armored limo they ride into the cult uprising, or perhaps your cult has already taken over their world, captured the car from the upper class, and gifted it to their leader. Whatever story you intend to give to it, I wouldn't recommend making a fleet of them. Such luxury vehicles would be the provenance of the wealthy elite and even then, most are probably not well enough armored to be of use in battle. Though I suppose you could always say that your cult is of the worker class from a minor Forgeworld that manufactured such vehicles and that is why they have a large quantity of them. That aside, as for the model itself, I would at least try to get rid of the super obvious 3D print lines even if you have to sand them down some. Looked like the had a quality issue until I opened it up. You could also add some armor plates to the forward heavy stubber hardpoints and weak spots like windows and the grill. Maybe move the main gun mount closer to the middle of the compartment? That one's more personal taste and battle effectiveness than anything else. I don't know the rules for Ridge Runners as I haven't played Genestealer Cults, but if it has firing points you might want to show them on the model somehow. Holes cut in the windows maybe, or if you put an armor plate over them a view port would work. it looks like it's a 3-man vehicle though, so that shouldn't be a concern. And of course, make a variant of the main gun for each option so you can switch them out as needed. Other than that, good work! You can design and print a 3D model which is more than I can say for myself right now.