You can't worry about being saddled with bad contracts, and technically, the Cubs were not as saddled as you think IMO. They were at the very end of those contracts, and the Cubs frankly could have kept them on the team and still not done any worse, or better. Referencing Corey Black for Soriano which to this point is nill, the others were Zambrano (1yr) for Chris Volstad, and Marlon Byrd (1yr) for Michael Bowden who offsets the Soriano deal in a big way. Dempster (1 yr) I can't remember, and Ramirez was already heading out.
Payroll has dropped significantly because they did not replace those guys with any equal dollars, but took the route of trying to replace on the cheap with somewhat equal talent. i.e., they still were able to tank.
And to take away any of your fear, have trust that the FO has instilled the waves of talent. That means that you should rarely if ever be saddled with bad contracts because you always have a farm system offsetting the larger contracts and making them more palateable.
The process they have been going through, was recovering from the "win now" campaign in 07' and 08'. It may be a long time before that happens again, and if it does, it probably won't be this front office that is doing it.
Sorry to get off topic, but they could easily pay 6/180 for Lester if they wanted to, and not hurt a bit in the wallet. Attendance would start to rise, merchandising would start to flip because of the buzz around the nation, and by the time Lester figures to not be that guy anymore, the TV contract would be well in place and they would be able to afford 3 more Lester's in the rotation if they wanted to.