I agree with MandiceP, they will be able to get out of those bars easy. I believe they are 1/2 inch wide, my gerbils in some spots would be able to get out. But the space is wonderful! If you buy it, you can buy a smaller mesh or something else to wrap around the cage from the outside. I tried mesh around my gerbils cage, but had a pull out drawer which I covered with boxes so they wouldn't hurt their feet. They ended up in tanks...
All of the smaller cages meant for mice are so small! I think you have a wonderful idea if you can alter it. Or, you could get a long tank with a topper on top, all costing about the same price as that cage. Same with the wires on the topper, you could put mesh or something. Good luck!
Betta's: "Mint" & "Flare-Boy"
Other:6 misc catfish,Tetras,Glofish,Mollies
*RIP* To all my past little ones