I'm not so naive to think this isn't a complex issue, but if you have someone willing to contribute to the tax base who isn't a criminal, I don't understand why we don't legalize them as quickly as possible.
I have no issues with immigration, but I think the qualifications for legal status should be slightly higher than being able to sneak past the border patrol. If lack of documented criminal history and the ability to step foot on U.S. soil are the only criteria, may as well just open the border.
This was my original point. If you say "all illegal immigrants (who haven't broken the law) can legally assimilate to become citizens" then you are basically saying, sneak in undetected, announce your arrival, and soon you can become a citizen.
But as sections of Europe are now discovering, there can be painful consequences to a very porous border. Communities can be disrupted, government finances put under strain, labor markets affected...
The success of immigrants (both themselves and for the society they enter), can depend on many things: the similarities in language, culture, skillsets and expectations they have. How much can they contribute in terms of skills and paying taxes? Will they be a net contributor or a drain on resources. Can they be a productive member of society?
FOR THE OP: Imagine you are in charge. You set immigration policies. Would you allow any illegal immigrants to quickly become citizens? What about future illegal immigrants? Where do you draw the line? How strictly do you enforce the border?