Hi bltomato,
Thanks for your inquiry.
With the current miGen jobtype, it is not possible to do what you describe.
In order to get the miGen jobtype to do that, it will probably need to be modified to
use frame-to-frame dependencies.
I'll have to log this as a feature request for a future version of the jobtype.
In the meantime, you will have to manually submit a separate job to render the
first few frames (perhaps at a higher priority too), so your artists can have a
preview of those frames quicker.