We are an European based company and we have two production gang programmers may fit your need, please kindly visit our web site at:
MP8011A, a gang socket programmer (1 to 8):
inDART-One, an universal in-circuit programmer (gangable solution, up to 32 instruments can be controlled by ONE PC)
Both instruments has free dedicated GUI or mode for production, and low skill worker could also press the START push button only.
On the other hand, please PM me if you need a contact for volume production in China.
Of course, you have to consider the security issue if you out source your production to third party.
Smile,