per-system control of "empty" Staff removal?

[Kieren MacMillan]

Hello, all --

I'm trying to hack control of the removal of "empty" (multi-measure  
resting) staves on a per-system basis.
What I've come up with so far is included below.

Can anyone think of an easier or more efficient method?
Considering how many voices/staves I'd potentially have to fake this  
way, I'd love it if something like

        \override Score.VerticalAxisGroup #'remove-empty = ##f

actually worked (from the example, I can see that it doesn't),  
especially on a Staff-by-Staff basis.

Thanks!
Kieren.
______________________________

%%%   CODE SNIPPET BEGINS
\version "2.9.9"

\layout
{
        \context { \RemoveEmptyStaffContext }
        \context
        {
                \Score
                \override VerticalAxisGroup #'remove-first = ##t
        }
}

musicA = \relative c'
{
        \repeat "unfold" 4 { c1 \break }
}
musicB = \relative c'
{
        R1
        \override Score.VerticalAxisGroup #'remove-empty = ##f
        R1
        << { \oneVoice R1 } \\ { \hideNotes c1 \unHideNotes } >>
        R1
}

\score
{
        <<
                \new Staff << \musicA >>
                \new Staff << \musicB >>
        >>
}
%%%   CODE SNIPPET ENDS