235/55r17 gives you the same circumference and radius as the 215/60r17 that you run just now (to within 1mm). It's also a factory fit size, used by VW. So no adverse effect on gearing by doing this. Personally, if it was me, for towing a caravan regularly, I'd stick to the standard size circumference atleast.
Its perhaps all about risk v reward. My own plans for the van, mean I'm playing the long game, so mechanical sympathy is a priority. Hence why I'm refraining from a remap. I do however run Amarok 18" wheels and run a tyre that's a tiny bit oversized in aspect ratio. 6mm (245/50r18). Putting that in perspective, by the time the tyres are ready for the bin (sorry.....recycling), they'll be worn down to the same radius as new standard sized tyre. But, maybe I just have overly sensitive arse cheeks, but I notice the difference in gearing even at that. Some members on here run 12 mm bigger radius. Some swamped stuff have monster aspect ratios that would stop me sleeping at night. I'm not brave enough to go beyond the 6mm.
Fractionally better for comfort and aesthetics but fractionally worse for your DMF/clutch pack. Makes me drive very gently, most of the time, thinking that. Would give me a migraine though, if I was lugging a tin tent on my towbar.
Horses for courses however. For example, your maybe planning to move the van on sooner than me. Have outstanding confidence in VW engineering being vastly superior to anything else like say, French or...... even Italian, perhaps.
Just my thoughts
.