I really do not see why anyone would make another person run his/her GPU mining equipment . First of all the process of setup your own GPU's rig is pretty easy + when he/she want to cash out money they do not need to wait for a full month . With most mining pools you can cashout every day if you want . the only thing you have is low electricity and it is in Russia because I do not think $0.10 is cheap .
I would choose to have my equipment in front of me and be able to cashout anytime I want rather than save few cents on electricity .
There is 0 reason to risk my money to save few cents even dollars .
You are right absolutely, if you have 1-2 farms... But if you have 50-100 farms, where will you put them? And how much time you shuld lose for monitoring and maintenance? And of cource will you have space with air conditioning and power supply?
Few people would build "50-100 farms" without already having a place in mind to run them...
So essentially, your service could appeal to those planning to build or expand their mining operation. Then you get back to the issue of trust; would they rely on you to care for the large hardware investment that they plan on making?
At this point, the answer is no.