I've tried to remove the stage as well and this is what I found out:
there is a business rule on the table sc_request: "Cascade Request Approval to Request Item"
this will set the stage to "request_approved" for all request item with stage="waiting_for_approval" (which is the default value, don't mess with this or your workflow won't start)
on the table sc_request_item there exists a Business Rule "Start Workflow" with the condition current.stage=='request_approved'
in the table wf_stage there exist two Stages: "Request Approved" and "Request Approved" not associated with any workflow
as far as my understanding goes according to this wiki page Workflow Stages - ServiceNow Wiki
if a stage is set on the request_item it will added to the "Stage-Workflow"
in the table wf_stage there exist two Stages: "Request Approved" and "Request Approved" not associated with any workflow
I'm guessing you could set another stage in the business rule sc_request."Cascade Request Approval to Request Item" and have change the condition on the Business Rule sc_request_item."Start Workflow".
I stopped here. Although there are just two small changes, you first you have to find out, if the stage is used anywhere else and I'm guessing there is a good chance that in future releases any script might refer to this stage as well.
