You might want to do a bit of research on reverse engineering and how memory dumps/footprints or analyzing file structures and formats etc. is going to take things to a whole new level for someone in the know.

A head start is a head start and any serious game developer is going to burn mucho dinero even in just three months. I never said that anyone would code a full game in three months. Stop pulling stuff that I never said out of your ass, kthx.

Also: The positive reception of the leak alone is a very valuable information asset for third parties (and thus a potential problem for Square Enix). It is true that other games have combined stealth, action and dialogue but some games worked for the audience and some games didn't. It seems like DXHR is going to be one of the working cases. That info alone is worth a lot because it's going to make copying the essentials much easier. I'm almost tempted to bet real money that some Eastern European or Russian devs are all over the DXHR leak already to produce one of their infamous clones.