This is a great thread, I think there are so many good ideas to improve existing designs. I have ARS racks and have actually cut and welded transition levels myself out of steel followed by painting it to match. It came out really nice, but one thing I realized is that there isn't much mark up on an ARS rack when you take into consideration all of the components, which is hard to believe since they sell for about $3,000 per rack.
There are a couple things I'd like to see, how about a rack system that you can buy one tub at a time and stack it together like Tetris. People would just buy it little by little instead of having to throw out thousands of dollars to buy a whole rack. I know you can do levels but it would be nice to have a way to buy just one tub at a time.
How about a fully enclosed rodent system similar to an ARS rack that has four sides, a clear front, and fans with carbon filtration to keep the smell to zero! I actually threw a tarp over my rack once and put a big carbon air filter on one end, the smell went to zero even though it was cleaning day and there was considerable smell. You could even sell aftermarket parts that add on to an ARS rack to convert it.
The problem with most of these ideas is that they cost more money than people want to spend. Just look at all the racks people are buying, not many people talk about ARS or Freedom Breeder because they want the most rack for the money, meaning they buy cheaper racks. I think no matter what you build there will be a niche market for it. I've actually considered building racks similar to ARS but if you look at the ARS operation on the web you can see just what really goes into it. You need a large warehouse and a large team of people, lots of storage space, a way to ship them by truck. And large racks can easily get damaged in transport, etc... You're better off buying racks and breeding snakes LOL.