As I said, a lot of the players abilities would become completely wasted in an ODI team featuring 10 allrounders and a wicket keeper. The specialists would have balance issues, but at the same time, there's little point in someone batting #11 who isn't considered as specialist bowler. An ODI allrounders team would probably look something like this:
Watson
Gayle/Jayasuriya
Kallis
Sangakkara
Symonds
Collingwood
Flintoff
Oram/Bravo
Pollock
Hall
Hogg
Now there's pretty much no chance of Watson, Symonds or Collingwood bowling, and their opposition would have specialist batsmen of a higher standard. And at the same time, it'd be pretty useless having Pollock at 9, Hall at 10 and Hogg at 11 - their skills would be wasted while the opposition would have better bowlers. Their batting would become irrelevant. While an allrounders team would look very good on paper in ODIs, it really wouldn't work too well in practice.
Tests are a totally different story as I mentioned before, as you can utilise different bowlers in different conditions as the pitch changes character throughout and the match, and you can also make full use of your deep batting lineup by virtue of the fact that you can bat forever.