Aree, I've built something like this but from existing parts + some DIY elements and have gone on several bike camping trips with it. I use my setup to recharge my bike battery and a few small electronics. My first iteration of this was was super simple and required no understanding of wiring and stuff because I just used a Jackery, which met my needs. My next version is going to be much more DIY and I'm considering building my own battery set-up this time. I think there is a sweet spot between backpacking minimalism and motor vehicle camping that you can hit with a solar trailer, and would be glad to give you advice on what I use and how I've sized my solar needs. If you've already built yours, I'd be curious to see what you did.
That big awkward looking thing on the roof rack is a Kamprite tentcot, which added to the "camper" feel, but as you can see is kind of hard to carry. I had to build a DIY roof rack out of aluminum crutches to hold the tentcot and solar. My solar panel is mounted to the carry bag for the Kamprite. For my next one, I'm ditching the Kamprite and going with a lightweight camping tent that fits inside the trailer, upgrading to 160W solar and building the whole thing from scratch.