I wasn't talking about just "filling out" minor league rosters, but setting your organization for the season so you have each player at the correct level that means the ones with BL potential, and the ones that match up well with your coaching strengths or ballpark affects at the different levels and the ones that will make the team at each level competitive. So, yes...I could start with my RL team and just throw two catchers on AAA...but in many cases you're moving players up a step or two at a time. The game as it is doesn't prevent that, but does make it more difficult than it needs to be.
Look, I understand many here care little or nothing about their minor league teams and even less about any player that doesn't have BL potential. To them this change wouldn't make a difference...but for some reason WIS does have five levels of minor leagues, a majority of the players in the game are not even close to BL quality and WIS went so far as to have playoffs and awards at those levels. At some point someone there thought there was some importance to the minor leagues. In some cases, especially if you're rebuilding at the ML level you can get enjoyment from this game by playing/managing your teams at the lower levels. That's kind of ruined by others not trying at all to be competitive.
I just don't see the benefit of the current system as the same problems people here are suggesting might happen can and do happen anyway. Even the Rule V draft can leave a team under the minimum or without