Limit WIP for each workitem state instead of state-groups

 We have been experiencing with our Kanban boards, and, even when now we can set the WIP limit for each group-state (new, in-progress, closed), we're looking for some way of limiting WIP on each state. So far, it's like I should create a state group for each of the states a work item can be assigned (new, ready for development, in progress, implemented, being tested, etc.). Unfortunately I don't think that's a good option given the cost that implies in terms of maintaining the process (taking into account that Kanban looks constantly for the team to update and improve the process).