Within the last few days a series of "but what if they..." has come up in the Matrix tag, surrounding alternatives that the machines could use in order to not use humans. It has become completely ridiculous for two reasons.
1) The real question is why DID they use humans and the Matrix, not every way they could have avoided it
2) The questions have been rendered unanswerable in their present form because as soon as one is answered an almost duplicate is spawned from the hellfire of which these questions come.
Why use full brained humans as batteries?
In The Matrix, why didn't Machines use solar energy?
https://scifi.stackexchange.com/q/12248/3958
Is the basic premise of humans as a power source in The Matrix reasonable?
etc. Some have already been closed, but others continue to spawn.