There is not really any rack that is suitable to house a wide variety of species. Carpets Royals gecko all have differing requirements. racks are about averages. They are all basically the same and the same temps and same conditions this method is best suites to the same species. Perhaps a different rack for each species and perhaps you could find a ambient that worked for all you have so they could be in the same controlled room. But in the same rack it is more compromise than correct. To maintain correct conditions for each you would need different shape 'drawers' for each. separate temperature zones for each and humidity conditions too. At this point it would be easier and better, and cheaper to have separate enclosures, each one could be tailored to the requirements of each species.