That's how I started with mine. I cut the ribs out and filled the gaps. Took them to my fibreglass guy who explained it wasn't as simple as I thought.They would need to be pegged and filled to make them wider. I'd have to have them built up on the vehicle which could ruin the paintwork, plus the vehicle would have to be left with him while he did the job, which would be done in between his regular fibreglassing work, which meant potentially being without the vehicle for months. The arches were "lost " at some point. Don't know where they ended up. If I could get a facelift set cheap enough I'd just modify the arches as I did before and stick them on. They're not really any wider but are deeper. But I think may give the illusion of being far bigger if fitted without the rest of that hideous body kit. I'm sure the bodykit was modelled on a Ju-52 !!
The ones on that Evoque above are exactly how I had envisioned the arches I wanted made up for my Freelander about 7 years ago. That's how far back I started the now defunct project. I had my old blue V6 back then..................................happy days.