Glad you found the source code you'd customized for that function.
You're right that that particular function isn't nearly generic enough to be used on many people's cubes, so probably we won't include it in ASSP. (If other people disagree and think we should take this idea and add it to ASSP post here.)
Also, if you were to write those reports again, you could probably do it with straight MDX instead of a sproc. Something like the following would work:
StrToMember("[Time].[Date].&[" + VBA!format(VBA!dateadd("d",-1,VBA![date]()),"yyyy-MM-ddT00:00:00") + "]")
Or rather add two dates with a colon between and use StrToSet instead.