That sounds like a great suggestion, and at least one person has suggested it in the past.
In the mean time, you can consolidate space and hide & unhide the windows associated with a server by holding ALT and clicking on the Status Window switchbar icon.
In addition to this method, you can also write a script to show only channels with activity in them. /window -w $chan in an On Text and On Action event, and /window -h $chan when there are no new messages for a long period of time (using a timer or other method you desire).
I hope either of these work-arounds help until scroll bars of some kind have been added.