(Two more I just though of) 1) Quicktime and Real alternative support (if possible. If not, understandable) 2) Flash support (Allows flash to silent install OR already be installed (wihtin the firefox dirs) when Firefoxsilent.exe runs)
1) To be able to set firefox as the default browser automatically 2) a slightly clearer guide packaged w/ sof on where you need to put plugins, themes, etc.