In your example there's a first undersized UPS A, then another UPS B, then whatever combination of electrical devices which power usage exceeds UPS A. You say t

In your example there's a first undersized UPS A, then another UPS B, then whatever combination of electrical devices which power usage exceeds UPS A. You say this is problem. If you have said combination of electrical devices, and if you're assuming we're using an undersized UPS A + the combo of devices, why does the UPS B matter? If you're going to overload the UPS A you're going to overload the UPS A regardless of UPS B, no? Daisy chaining or not, that doesn't seem like the actual problem to a knee-jerk thinking.