Weight?
You should see these multiband 700/850/1900/AWS antennas. They're pretty big. (AWS uses a subset of the Band 1 2100mhz for the downlink, and 1700mhz band for uplink (the 1900mhz band used by Band 1 is already used for PCS 1900mhz service here.) I think you could stick those racks behind it.
I wonder about the total weight being loaded onto these if all the carriers start getting these huge antennas and racks of hardware on the tower though.
As for cooling... well, the traditional setups do burn lots of power. But, if you keep the actual RF hardware cool enough (hopefully it has a hefty heatsink), the elements that toss data around and do the processing? You've got these CPUs now pushing past 50gflops per watt, the power use (and heat production) of the rest of the system can be fairly insignificant. If worst comes to worst, and you've got to run the stuff in a cabinet... well, it should at least fit in more snugly with the generator and battery backup I guess and need less cooling.