Doing some strange stuff with multi-measure rests

[caagr98]

Basically, I want to show a rest with indeterminate length for all 
parts, except the drumset, which is to make undefined creepy noises, and 
the cymbal, which should do a drumroll-crescendo (not sure if there's 
any fancy name for that) before the rest of the parts resume playing.

I've attached an image of what I have so far, and one of what I want 
(which obviously is photoshopped).

Is this possible to do? (Or is there some better way to show it that I 
haven't thought of?)


(Mostly) minimal example of what I have:
```
\version "2.19.59"

mmrferm =
  \once \override MultiMeasureRestNumber.text =
    \markup { \musicglyph #"scripts.ufermata" }

\layout {
  \context {
    \Score
    \compressFullBarRests
    \override MultiMeasureRest.expand-limit = #1
  }
}

<<
  \new Staff { b'1 | \mmrferm R1*2 | b'1 }
  \new DrumStaff { b'1 | \mmrferm R1*2 | b'1 }
  \new RhythmicStaff { b'1 | \mmrferm R1*3/2 b'2:32\< | b'1\! }
>>
```
(In the real score I create a 'MultiMeasureRestEvent explicitly to avoid 
the barcheck.)

mmr-have.png
Description: PNG image

mmr-want.png
Description: PNG image