I was wondering if there is a way to stage 2 15 ton and one 5ton package units. If each unit had several stages could they be connected in a way that they would only kick on in the order needed? Can three units operate off of one tstat? Really one tstat, not hiding others somewhere. I know two can be twinned together. A store owner I know wants something like this. He also wants it to operate all off of one tstat. I need to think about this for awhile but I thought I might get some input from all you hvac genuises.