Since difficulty constantly rises and pools control more computing power than ever before the BTC/computing power will go down and so will the $/computing power if exchange-rates stay the same or lowers.
I was just wondering if the pool owners could re-program their system so that the computing power can be used for bruteforcing?

If it was possible they could just pay off all the bruteforce computing-power with the equal amount of BTC/share without the miner knowing a thing.

So, could this lead to a scenario where it is possible to buy bruteforce computing-power?