Can I use USB data pins as a power source?
This is neither Kosher nor Halal. It should actually be explicitly forbidden in the Electrical Engineering code of ethics. Some certification standards explicitly frown upon this.

Besides the wires probably being extremely under-dimensioned for the delivery of power, using narrowly-defined standard connectors for non-standard uses is a sure way to cause an unforeseen problem down the road. Particularly if this use would ensure the destruction of any standards-compliant device that could be plugged into it, as is this case. 

I have had apparently standard but mis-wired cables in my hand that have caused the malfunction and even destruction of standard-compliant devices.

Standardization bodies actually spend a lot of time designing their connectors so that these cannot be confused/mistaken/interconnected with anything else out there. Don't make our job harder.

Some connector types are more generic than others, stick to those.