Fair enough. Still you have no interest in why the Hammad cousins were in the WTC?
Occam's Razor: do not multiply entities unnecessarily.
We have two possible explanations for the WTC sprinkler system failing: the first is that the impact of each plane ruptured the pipes in the impact regions. This is a simple explanation. It is supported by reports of water flowing down the fire escapes--i.e., the sprinklers came on, but the water did not reach the fires because of the ruptured pipes.
The second possibility is that the Hammad cousins, who were apparently unlicensed plumbers, were able to perform an act of sabotage that, if detected prior to aircraft impact, would warn one and all that the building was targeted for some sort of attack. This violates the most basic OPSEC considerations, increases operational complexity (and thus risks failure of the enterprise), and is probably unnecessary (a fully loaded 767 is much more than the buildings were designed to withstand).
The first problem is that such an operation violates Al-Qaeda doctrine. Al-Qaeda has a well-deserved reputation for excellent operational security. Your theory disregards that fact.