Shortly, I will attempt to answer the question "What's the greatest possible baseball team one could draw from all of the players in history?" It's a tricky question. Usually, people put forth a player for each position with maybe a relief pitcher or two as well. I don't think that's enough.
Baseball teams are not judged so much on the quality of one game, but the quality of their pan-season (and post-season) performances. Great teams have the depth to overcome injury and the bench pieces to make the most of a high leverage situation, be it with a left handed specialist, a speedy pinch runner, or good defensive replacements. Top nines are fun, but baseball teams have 25 players on the roster and everyone of those can be used to improve the team's record across a season, even by simply providing a banged up starter with a day off and preventing a worse injury down the line.
So I read the question at hand as "What 25 man roster would have the best record after a 162 game season, assuming 81 games with the DH and 81 games without?" I'm going to assume that park effects are negligible and that home field advantage is negligible as well. Furthermore, I'm assuming that any call ups (due to injuries) would be roughly replacement level players. No leaning on the farm system here.
As a result, my bench selections will be made with either positional flexibility or a specific role such as base running specialist in mind. That said, I'm not going to completely neglect a player's other tools. All of the bench position players I select will be legitimate around players, but usually ones who have at least one outstanding quality that would make them useful tactical pieces such as defensive replacements. I'll also put forth a few alternative candidates for each slot.
I invite others to put together similar rosters. In fact, some friends are doing so, and we'll be rolling out the rosters, one slot at a time starting tomorrow, June 1st. Feel free to adjust the specialist roles or balance your roster as you see fit. I'll be rolling out my selections roughly in order of inverse play time. So tomorrow, I reveal my 25th man, the pinch running specialist. And no, it's not Vince Coleman.