Ok, got your point.
But sometimes I need to test libvirt guest when it is shutoff. I really prefer to do this work in env_process with some
params(such as start_vm=no).

In face there is another choice:
(1). introduce a new param named vm_status=[shutoff|paused|running]
(2). Add some code to parse this param as the following rules:
      a). if there is vm_status=None. Keep the start_vm and paused_after_start_vm working as before.
      b). if there is a param named vm_status. ignore the start_vm and paused_after_start_vm.

On one hand, we can keep the old config file work well as what they worked.
On the other hand, we can unify the vm status related params and do some more operations.

What's your opinion?