Here you go;
Create a template with name "Pending status". Set here the status to pending.
In the approval process under submit action set a fieldupdate for "Template Name" Here do an update with a formula like "Pending status".
Under Change create a new checkbox hidden from the form.
In the approval process under submit action set a new check box to true.
Now create a Process builder to set the status when this checkbox is true.
Theoretically, for the first step, it worked. But what about changing status after approvals and turn it to In Progress??
Same scenario only set the field update on Final approval, final rejection step.
Does that make sense?