Knowing how many of the smaller tanks with built in filtration and lights my LFS
sells I can see it working if you can price it right. At least it will be a functional product with the T5 lighting as opposed to some I've seen.
The problem with anything like this is going to be marketing it enough for people to want to buy it. Can it sell? I think so from what you have. Will it? That is hard to say. Perhaps build one and take really good pictures and post it up for sale and see how it does. That right there will give you a good idea.
Also think about shipping for those who aren't local. There will be some who want it shipped. You can also get with your LFS
and see if they are willing to share in the profit if willing to have one or two displayed and for sale. You can always charge a little more for those to make up for the split the LFS