Hi Josh,
I don't have an authoritative answer for you, but you MAY be able to accomplish what you're after by modifying the ParentId and TabOrder property of the relevant admin tabs directly in your database (the admin and host pages are stored as rows in this table just like any other page). You'd have to do this on a per-portal basis.
The reason I am equivocating a bit is because I know that you can't nest the admin/host menus more than one level deep. I tried awhile back to do this -- by putting some of the less commonly used functions in an "Advanced" option under the admin menu, but there was specific DNN code that didn't like this.
So, give it a shot and see what happens. But please back up your database first!
Finally, since I hear that DNN will allow admins to treat the admin pages as "any other" page, I suspect you'll be able to much more easily accomplish this task in the DNN 5.0 timeframe. So you might just want to wait a few weeks.
Hope this helps!
Brandon