Workaround: let P2 use P1's menu buttons for changing P2's own difficulty, but only when P1 isn't around.

stepmania/src/ScreenNetSelectBase.cpp

@@ -11,6 +11,7 @@
 #include "MenuTimer.h"
 #include "NetworkSyncManager.h"
 #include "RageUtil.h"
+#include "GameState.h"
 
 #define CHATINPUT_WIDTH				THEME->GetMetricF(m_sName,"ChatInputBoxWidth")
 #define CHATINPUT_HEIGHT			THEME->GetMetricF(m_sName,"ChatInputBoxHeight")
@@ -169,6 +170,11 @@ void ScreenNetSelectBase::Input( const DeviceInput& DeviceI, const InputEventTyp
 			m_sTextInput += c;
 			UpdateTextInput();
 		}
+
+		//Tricky: If both players are playing, allow the 2 button through to the keymapper
+		if( c == '2' && GAMESTATE->IsPlayerEnabled( PLAYER_2 ) && GAMESTATE->IsPlayerEnabled( PLAYER_1 ) )
+			break;
+
 		if( c >= ' ' )
 			return;
 		break;

stepmania/src/ScreenNetSelectMusic.cpp

@@ -339,6 +339,14 @@ void ScreenNetSelectMusic::MenuUp( PlayerNumber pn, const InputEventType type )
 
 void ScreenNetSelectMusic::MenuDown( PlayerNumber pn, const InputEventType type )
 {
+	/*Tricky:  If we have a player on player 2, and there is only
+	  player 2, allow them to use player 1's controls to change 
+	  their difficulty. */
+
+	if ( GAMESTATE->IsPlayerEnabled( PLAYER_2 ) && 
+		!GAMESTATE->IsPlayerEnabled( PLAYER_1 ) )
+		pn = PLAYER_2;
+
 	if ( GAMESTATE->m_pCurSong == NULL )
 		return;
 	StepsType st = GAMESTATE->GetCurrentStyle()->m_StepsType;