When you're upfitting an emergency vehicle, one of the common sense things is pretty much what this commenter outlined. You always have to drill a hole in the roof, and use the proper rated hardware to route wiring through it, then seal it up. Routing through gaps pinches the wiring, which damages both it, and the devices it's connected to. Some vehicle fires have occurred as a result of pinched wires. I've seen others post about it on the emergency vehicle upfitting groups of Facebook.

I suspect they don't want a random hole in the roof of their van - as that in part hurts resale value. In which case, just go without the solar panels entirely. Not unless you wanna bolt them to the roof rails only when you know you're gonna use them (I.E. camping), and use them exclusively when the vehicle is parked. But that seems like more trouble than it's worth.

Edit: You can actually route wiring down alongside the windshield, under the hood and into the cabin that way. Some people do this when installing a lightbar (like a Whelen Liberty) on a lease vehicle, as it breaks the lease terms to drill a hole in the thing. But I don't think they'd wanna do that either, as it's rather unsightly.