Issue with Accept Task smart service

a) I wouldn't make the user a Sys Admin just to accept the task. I'd make him or her a Manager (or higher) of the process instance.
b) Right, this is getting into a complex / subtle area of how process security works. You can't "make" someone an initiator of a process, unless he actually initiated a process. If you are inclined to play with the APIs, I would recommend just creating a revised version of the Accept Task service, which takes in a username as an input, then accepts the task as that user. (You have to initiate ProcessExecutionService as that user context, in Java, instead of using the default Service Context that's passed into the node.)

a) I wouldn't make the user a Sys Admin just to accept the task. I'd make him or her a Manager (or higher) of the process instance.
b) Right, this is getting into a complex / subtle area of how process security works. You can't "make" someone an initiator of a process, unless he actually initiated a process. If you are inclined to play with the APIs, I would recommend just creating a revised version of the Accept Task service, which takes in a username as an input, then accepts the task as that user. (You have to initiate ProcessExecutionService as that user context, in Java, instead of using the default Service Context that's passed into the node.)