Moral of the story, if we legalize the folks who are here and set up a guest worker program, they will demand prevailing wages and benefits, so we gain nothing but a bigger population and a bigger drain on social services.
Here's my solution (well, not really mine but piece meal from other places, but anyways). Step 1 - shut down the southern border for real with troops and walls. Step 2 - give the illegals who are here 4 months to identify themselves. Those who don't identify themselves go to prison for 5 years before getting deported when we catch up with them. Step 2 - figure out how many illegals are upstanding, send the rest back, send the really bad ones to jail. Step 3 - Give the employers 3 months from the end of the 4 to come clean. Step 4 - now, with the employers having to pay fair wages, see exactly how many low level employees we need. My guess is not that many since we have a 4.7% unemployment rate, not a ZERO% rate. Step 5 - create a guest worker program to accomodate that need.
I've been giving your question some thought. First, I think there would be serious ex post facto type difficulties making illegal alienhood a felony for those already here. For new arrivals, possibly, but for those who are already here taking their current condition from whatever it is to felonious is probably not going to fly legally.
Second, I'd approach the matter this way - I'd make the conviction of the newly apprehended a matter of deportation with the threat of immediate incarceration as a felon upon return.
Third, for the 12 million or whatever already here I'd offer an amnesty period within which they may go through the existing legal procedures or face immediate deportation. That's within existing law and I don't think we'd have any ex post facto problems with it. They play by the rules, they're in; if not, not. If they have to wait elsewhere while a quota is in operation let that quota be first come, first served (also within existing law).
To stabilize the situation I'd deploy national guard units until a suitable barrier is constructed. Sorry if that looks like an Iron Curtain - it isn't. States have an unquestioned right to the control of both border and immigration and we've lost control of that under the existing conditions.
It isn't a perfect solution but it's better than one side shrieking at the other. IMHO. What do you think?