They could sack him for Gross Misconduct and Alonso's lawyers couldn't say jack. It would look good in the papers too as it would at least indicate that McLaren firmly blame the individuals involved in the scandal and don't feel guilty as a team as a whole.
We all know that Ron would prefer it if Lewis won anyway - so considering what Alonso has done to the team why not just sack him now and pretty much guarantee Lewis' victory?
What have they got to lose? They've already lost all their Constructors points! It's all about that Drivers title now and I really can't imagine ANYONE in McLaren right now wanting that to goto Alonso.
They have not even sacked Coughlan yet, so no surprise Alonso ain't been asked to leave, but your right, if they did sack all those involved it would certainly leave a less bitter taste in the mouth and McLaren could well come out of it looking not too bad, that is off course if these are the only ones involved which seems a bit unlikely.