I built a bicycle camper trailer 13 years ago, with a full-size bed, kitchen, toilet, shower, water tank, solar, overrun brakes and everything. All my photos were on Photobucket, which pulled a fast one on everybody 8 years ago so I lost them all. But there are still photos of the construction floating around on Pinterest, from people who copied them before Photobucket pulled them:
Amazingly, I managed to keep the weight under 120 lbs. So it wasn't outrageous considering all it could do.
But here's the thing: I went on a 300 mile tour of the Netherlands with it. Guess what happens when you hit the slightest hill with 120 lbs in tow, even with extra-low gears and even in the Netherlands: you wish you had a lightweight tent and a few euros to hit the next campground when the sun goes down. And even on a dead flat, smooth road, the extra drag due to air resistance and tire resistance is very noticeable. And I'm not even talking about hairy windy days: anything about 30 mph wind is friggin' alarming.
I would NEVER ever consider bicycle-touring with any sort of trailer ever again. It would only make sense in a desert with a nice, low-resistance, flat ground like the Bonnevile Salt Flats, but zero facilities for hundreds of miles around to justify towing all that stuff.
In other words, a bicycle camper trailer is a solution that solves a problem that simply doesn't exist. You can have all a camper offers with traditional camping gear without paying a stupid speed penalty and being a danger on the road. And if worse comes to worst, a credit card is only a few grams and it buys you a hotel room with a shower, if camping just isn't feasible.