I think this would be a step in the right direction. Take todays Wolves v Man Utd game for example. I'm not saying Wolves aren't trying, in fact they are playing fairly well with 10 men all things considered, but in general it would give sides that go three or four down a real reason to fight on.
It would reduce the outflow of fans early from games that are very one sided. Towards the end of the season it might make the relegation battle more exciting, the knowledge that a rival club could drop a point by getting a serious beating. Don't forget Man United, Arsenal and Spurs have all been beaten by 5 or more in the League this season, so it does happen occasionally to big sides too.
Fiorentina were awful last night at home to Juve even considering they were down to ten men and were 5 down with a full 18 minutes to go, and i watched Lazio being taken apart by Palermo a few weeks ago, both clubs that would usually harbour some hopes of European football (note Lazio scored at the end to "only" lose 5-1). So you you could not just take 3 points off a rival club with European aspirations, you could gain 4 on them. The crowds flowed out of the ground very early after the Fiorentina game,whether the potential of the humiliation of a docked point could have kept things more interesting. So maybe i will submit this idea to Sepp and Co rather than just the Premier League
I think it would keep things a bit more interesting at both ends of the table!