Why football should scrap the triple punishment rule

You spend two months waiting for some Champions League football, then the laws of the game ruin two matches in as many days. After Manchester City lost 2-0 to Barcelona on Tuesday night, Samir Nasri said City could still go through but, as Roy Keane might put it, he doesn't know what he's talking about. The game was up for Nasri, his team-mates and everyone watching as soon as the referee pointed to the spot and waved a red card at Martín Demichelis.
These matches are won and lost by finest of margins but a law that reduces a team to 10 men and then makes them face a penalty is extremely harsh. The punishment doesn't fit the crime. Demichelis made an error of judgement and mistimed a tackle on the edge of the box. He didn't endanger his opponent's safety; he just tripped Lionel Messi, who was able to pick himself up, walk a few yards closer to the goal, place the ball on the spot and kick it past Joe Hart to give Barcelona a crucial away goal.
That should have been enough punishment for City but the laws dictate that Demichelis had to be sent off for denying Messi a goalscoring opportunity. The penalty was a just reward for the foul but the red card altered the whole spirit of the tie.
Manuel Pellegrini was forced to make a double substitution and reorganise his players into a solid defensive block for the rest of the game. A match that had been genuinely exciting in the buildup and opening stages became a battle of attack versus defence. City's only consolation is that this triple punishment rule has a final layer of judgement: Demichelis will be suspended for the return leg.
Arsenal suffered a similar fate against Bayern Munich on Wednesday night. David Alaba may have sent his penalty off the post and wide but the referee's decision to send off Arsenal's keeper robbed us of Santi Cazorla and a decent contest between two teams aspiring to win the match.
What started as a fascinating, end-to-end Champions League encounter became a slog for spectators. Arsenal had 12% of the possession in the second half, completing only 62 passes to Bayern's 508. The game looked more like a Sunday League walkover than a high-end meeting in Europe's premier club competition. It was nearly enough to make viewers turn over and watch the Brits.
There must be a way to fix this. How about limiting the punishment for players who concede penalties to yellow cards (unless they're guilty of violent conduct)? Perhaps the defending team should be given the choice of losing the guilty player or conceding a penalty goal. Anything that would stop games from becoming unwatchably one-sided would be welcome.

There's always two sides to the story. DGSO outside the box is a straight red and that is how it should be. Inside the box, then it is a double whammy. Just supposed for a minute that it was a pen and yellow card. Let's say I round the keeper and just have to tap it into an empty net and then a defender trips me up. He knows he's only going to get a yellow and at least the keeper might be able to save the pen or the pen could be missed. Better odds than the attacker just tapping it in from 6 yards with no keeper to beat.

The triple whammy is hard to take. Keeper sent off, pen given and outfield player has to be substituted so the 2nd keeper can come on. Maybe in these circumstances, you could award the pen and give the keeper a yellow card but then you'd be treating the keeper differently to an outfield player which isn't right.