If you like the 520 I don't see any reason not to upgrade it with new wheels to get specifically what you want. Unless there's a problem with the components, keep them. They were quality when made. You can buy a 700c wheel with a dynamo, a 700c rear wheel (any 11 or 8-9-10 speed wheel can take a 7 speed cassette with a spacer), and since that will make your wheels a little smaller it will give you about 4mm more vertical room to install fatter tires.

I don't think you can expect to get bikes this good today, plus the accessories you want, for $1200. A 520 today costs $1260 MSRP. A name-brand gravel grinder with any pretentions to being nicer and more modern than that will run you up to nearly $2000 once you add the lights.