I think, as a backwards-y compatible-y solution... the handling of %!variable would look like this. (As pseudo-coded in mSL for clarity)

Code:
; where $1 is the word being parsed.

if ($left($1,1) == %) {
; this is a variable.

  if ($mid($1,2,1) == !) {
  ; this might be a variable name OR it might be a delayed evaluation.

    if ($var($1,1).local) {
    ; %!variable is a literal local variable name, so let's evaluate it without delay.
    ; (compatibility mode)
      return $eval($1,2)
    }

    elseif ($var($regsubex($1,/^%\K!+/,),1).local) {
    ; %variable (without !'s) is a known local variable, so let's delay evaluation
    ; by removing just one '!' from $1 (eg: from %!!!variable to %!!variable) (new mode)
      return $regsubex($1,/^%\K!/,)
    }

    elseif ($var($1,1).global) {
    ; %!variable is a literal global variable name, so let's evaluate it without
    ; delay. (compatibility mode)
      return $eval($1,2)
    }

    ; else { ; since no known (local or global) variables exist by this name
    ; (eg: %!!!variable) then let's treat it as a delayed evaluation.  (new mode)
    return $regsubex($1,/^%\K!/,)
    ; }
  }

  ; this is just a variable name without '!'.  so try to evaluate it. (as usual)
  return $eval($1,2)

}

Well. At least I won lunch.
Good philosophy, see good in bad, I like!