We use statuses in phabricator a lot and they act as the truth, so the view in maniphest that groups by status is very important and shows the health of the project.
I can't think of any reason to build this since most installs use only "Open" and "Closed" status, can you explain in more detail how you use Phabricator? Specifically, the drag and drop stack is built around Priority (and sub priority) editing.
https://secure.phabricator.com/book/phabcontrib/article/feature_requests/
We don't have plans to implement this, mostly people use Projects/Workboards to better indicate "status" of a task other than Open and Closed (In QA, Out for Review, etc). If you have a specific workflow you'd like to tell us about, please feel free.
We started using Phabricator when workboards were in prototype so we created all the statuses that we use for a ticket in Maniphest such as:
in dev
review
merge
qa
uat
live
etc.
We have been using this along with the reporting feature in Maniphest to track the progress of a project. Perhaps we should remove all of the maniphest statuses back to default (open closed) and start using the workboards to show the various states a task is in while it is open.
I don't think we will be able to report on the workboard statuses though, so if we want a report on a certain project, we would then have to go into the project and look at the workboard...which is the same result as running a report I guess.
T5793 is "Personal Workboards" which would be a set of columns for just you. T5474 is "Column Triggers" would provide running of commands when you drag stuff into a new column.
Mostly, we'd probably pursue these options which solve lots of problems (triggers could automatically change the status on dragging, for instance) instead of spending more time in the normal Maniphest display.
But mostly Workboards are a good way to share this data at a Project level vs. just your task list.