The one way I did this in the past is setup a token in the user data for the drop down validation to show what request status you want to show that row on. Then create a SQL validation that will dispaly rows based on the status. Use that SQL validation in the request type token.
In 7.1 this is difficult and would require a combination of the use of user data and rules. I believe there is a knowledge base article for this with instructions. Essentially, by assigning user data to each value, you can drive when the value appears by tying the status value to the list value's code or user data. So you could still use a single list. Given the customization required, you'd be best advised to wait for 7.5 where the UI logic rules should allow this to happen more easily.
We have not tried implementing this yet, so I'd be interested to hear how you make out. Please let me know - email@example.com. Thanks.
I was facing issues when was using the [REQ.STATUS_NAME] token, somehow I still have that,the rule does not validate against the token.
Instead I created a user data with Request Status, I used 'sql validation' and used the token [REQ.REQUEST_ID] to find the current status for the request and then map it to the user data to get the values populated.