In the current redmine version are two option possible for the @% done"@ ration:

• via user selectable pulldown menu
• via ticket states.

Via ticket state mode the percentage value can be left empty.
In the documentation "Issue statuses":http://www.redmine.org/projects/redmine/wiki/RedmineIssueTrackingSetup#Issue-statuses its documented:

bq. As per screenshot below, you can set the % Done for each status - (if left blank, changing an issue to this status will not change its percent done.)

Would it be possible to enhance this with another option?
If the @% done@ is left blank, redmine will display the pulldown menu like in the mode via user selectable drop down menu?

This would give the option, that a developer can adjust the @% done"@ in some states.
But if the tickets will be set as an example into 'QA' issue state get an fixed value.
The same is can be done for the closed states.