Akhtar is a good pick, I'll admit that but he couldn't sustain it.
Marshall wasn't anywhere near as devastating in ODI cricket as he was in Test cricket. Dennis on the other hand adapted much better to the format.
Imran Khan. I'm not going to lie. I would have loved to have had him in my team. Second best ODI all rounder, and you have the first.
Flintoff, good all rounder but I think he weakens your batting line up as you already have Imran in the top 5. Two batsmen with an average below 35 in the top 7 doesn't make for good reading.