A Box Bicycle as a City Bike Replacement?

First off this morning, I wanted to share a quick reminder about the Team World Bicycle Relief fundraiser started by Barb Chamberlain of Bike Style Spokane. While we haven't seen a ton of support for this particular team, I just want to say that anything you can donate is beneficial - from $1 to whatever amount is affordable for you and your family. If you can donate by December 31, 2011, your contribution will be doubled, which is absolutely amazing. So, truly, if this is something you've been considering, please do take the time to share what you can. You can donate anonymously, or using your name, and feel free to use my page linked above, or the main team page - whatever makes you comfortable. Thank you in advance for your generosity!
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While it seems a bit strange to go from donations to wants/desires, I suppose it is a part of how my brain works. I absolutely love to give, but I also have the side of my brain that gets attached to something and then has a difficult time giving up on it. While my hunt for the elusive "perfect" city bicycle continues, I've added a new obsession to the list: a box bicycle. At first, I just thought they were interesting to look at, but never thought they were something I would actually want or need, but lately, I've been pondering the possibility that it might not be such a bad idea to have this type of bike. I've even thought that perhaps I could combine my need for a city bike into my want of a box bike. Could this actually be possible?

Image from My Dutch Bike

I should start by saying I have never in my life taken a box bike out for a test spin (though I sense this is in my near future), and I might completely dislike the way they ride; however, the idea of this bike absolutely fascinates me and I think it could be quite practical. My first thought is that 90% of the time when I am riding a city bicycle, it is to fetch something from the market, other stores, or to haul something, so having the space to pick up groceries, dog food and other various sundries seems to make sense. Currently, I don't have a bike that I can haul a 40lb bag of dog food home on (at least not without having a near death experience), so I find myself driving the 3 miles (6 round trip) to pick it up, which makes me crazy. With groceries, I tend to buy far less when on the bike, or forget things, and while I don't mind making multiple trips in a week, there are simply times when we need to buy more food in a single trip (such as during the holidays, for parties, etc).

Image from Christiana Bikes

While I do realize most people purchase this type of bicycle to take their small children with them, because I do not have two legged kids, I also thought it could be a means to haul around my four legged, furry kiddos. I'm not sure that the box is actually large enough to hold all three of them, but from what I've read, there are some that can hold up to 220 pounds of cargo (such as the Christiana above), which would certainly be enough for my 175 pounds of dog (plus their water, balls for fetching, leashes, etc). Getting them to stay put in such a device might be a challenge as they (particularly the Labrador) are very fidgety animals, but I think it could be worthwhile to be able to avoid the car for trips to the dog park for exercise.

Image from Avenir

I do realize that getting a removable cargo carrier of some sort probably seems more practical, but I have yet to find one that can hold the weight that it would need to in order to be practical for all purposes in my mind. Thus, I am finding the idea of this box bike more and more appealing. Have I completely lost my senses? Perhaps. What do you think? Has anyone out there thought about a box bike for purposes other than transporting children? Perhaps you currently use yours as a hauler of goods rather than people? I know there are many people using these now in the States, so I'd love to know more about personal daily use in areas that aren't necessarily flat. One of these days I will make it to the bike shop to actually try these out, but in the mean time, my mind has been wandering and the idea doesn't seem as far-fetched as I once thought it to be. Feel free to tell me I'm crazy (I assure you, it won't be the first time I've heard this statement), or to add your thoughts on the matter.

Updated to add:
Reader LuckyChow99 sent in a photo of an ingenious dog carrying device he made last year. I know I'm not the only one who struggles with how to carry larger dogs, so I thought this information could be helpful to others. Here is what he had to say about the construction.

"Here is a cart I made from an old childs trailer. I used the frame and placed 1/2 inch plywood over it and then covered it with a rubber sheet. I put tie downs around the perimeter so the crate can be clipped in on the corners with simple snap hooks. This keeps it on the trailer, no matter what. I simply put a 36" crate on top and away we go. I'm pulling it with an electric bike I previously owned. Savannah is very comfortable in a crate, as that's how she travels in the motorhome. She loved it!"

Thanks so much for the information. I think this is a very interesting creation that seems to work well... and of course, now I want to try it out for myself. :O)