The immigration issue really comes down to three elements:
(1) Objectives. Whom do we want to let into in our country and whom do we want to keep out? For those already here but without permanent status (i.e. permanent resident alien or citizen), whom do we want to let stay in our country and whom do we want to keep out?
(2) Enforcement. How do we enforce this? That is, how do we keep the people out whom we want to keep out and how do we get rid of them if they get in anyway (or are already in).
(3) Documentation. For those whom we want to let in, how do we keep track of them and their status? This is important for making certain that those who are here temporarily leave when their time is up, for making certain that there is a clear path for permanent residence and/or citizenship for those whom we wish to add to our country, and for making certain that those who are here temporarily but indefinitely (e.g. those who need to get their status renewed) get processed in a timely manner.
The problem with guest-worker programs and the like is that they are based mainly on the notion that documentation is the only problem. That is also why "undocumented worker" is not an appropriate term for an illegal alien. It implies that they simply did not obey the technicalities of coming here. It ignores the fact that there are reasons why we don't let everyone in who wants to come in.
Enforcement is a necessity. Unless you want to let absolutely everyone who wants to come in in, you have to be able to stop people from coming in using non-official channels. If someone wants to come in for nefarious reasons (drug runners or terrorists or other assorted criminals), a guest-worker program designed to get people who would otherwise come in illegally "in the system" will not get them into the system, because their interests in coming here are themselves outside the system. Without some way to keep them out, they will come in illegally, guest-worker program or no.
But really, the primary issue (and the one no one wants to discuss) is objectives.
Whom do we let in (let stay) and whom do we keep out (kick out)? Until we address that issue, we cannot have true immigration reform.
That is all.