Stephen Waugh wasn't that good a one-day player, simple as. 30 was never that good an average, was merely passable.
And it's not true at all that most players with good First-Class grounding succeed at OD cricket at all, they need the skills, and those skills need to be developed at an early age.
As I say, England picking domestic failures is the problem. There is far less domestic one-day cricket now than there was 5 years ago and more as I've already said. But overkill of domestic one-day cricket won't turn good OD players into bad ones. The problem is that there just haven't been enough good OD players in recent times, and quite a few of the few good ones there have been have been ignored in favour of very poor ones.
You want five bowlers and six batsmen, including your wicketkeeper, no need to overcomplicate matters. Some of those bowlers should obviously be able to bat, ideally three at least. If those five bowlers are seamers or three seamers and two spinners, good, but don't prejudice it for what style they bowl.