If (and that's a big if) I were to allow this alternate ability that lets you take feats without prerequisites, I would only allow it as follows:
For the bonus feats at first and second level, you may ignore ability score prerequisites only. You must still meet all feat, BAB, and other prerequisites. For the bonus feat at sixth level, you may ignore ability score prerequisites and one feat prerequisite, but must meet BAB prerequisites and multiple feat prerequisites.
For example, if a monk wanted to take Spring Attack as their bonus feat at 6th level, they could ignore the 13+ Dex requirement, but would have to have either the Dodge or Mobility feat (but not both). This should cut out the cheesiest abuses while still opening up enough opportunities to be worthwhile. Plus, this is exactly in line with the prereqs normally ignored by the monk. Under no circumstances should anyone ever be allowed to ignore BAB or skill rank prerequisites, which is an important level-limiting mechanic.
You are just making monks worst, because he would still never qualify to rapid blitz and stunning fist would be out of question.