First of all, I wasn't talking about easing up on enforcement for those six months any more than we currently are, so it wouldn't give them any more "window" than they have now. Secondly, if they tried to come here through the illegal route by that time, that would be the worst decision they could make for themselves, because they'd be getting here and getting set up just as the heat would be starting to rise, and it would be rising without letup. Their stay here would wind up being quite short. It would be far more in their interests at that point to register with the guest-worker program. Why deal with coyotes (both the human and animal varieties), rattlesnakes, the harshness of the desert weather, and ultimately, the strong likelihood of being caught and sent back and having your efforts all be for nothing, when you can instead go down to the local consulate and apply to get in legally?
And a strong show of force at the border is something we're going to need to do anyway, even if we go with your plan (and even if it will work as well as you claim). It's much too porous as it is, even without ordinary workers trying to get in.
If you give employers a 6 month window for hiring illegals, you are giving illegals a 6 month window to come here. We don't even try to keep illegals from working here. In fact, some local gov'ts even encourage it.
I don't care how much money you spend (of taxpayer money), if you have willing employers and willing employees, you can't stop it.