He never said he was going to deport all of them. Now the question is how is this resolved in a way that will not create additional incentives to come illegally.
IMHO: This is how it should go.
1) Secure the border.
2) Fully implement E-Verify
3) Remove all convicted illegal aliens and all convicted legal aliens who are subject to removal through an expedited process.
4) For all non criminal aliens who entered illegally or overstayed a legal visa offer two separate programs.
Program A: For aliens who just want to work here and eventually go home. Offer a low cost expiated process to adjust their status to that of a 'non-immigrant' guest worker. Under this status there is no pathway to becoming a lawfully admitted permanent resident alien (LAPER) or a pathway to US Citizenship.
Program B: For those aliens who have been here for a long time and have demonstrated good moral conduct and are not nor likely to become a public charge. They may submit an application to adjust their status to that of a Permanent resident.
This will not be an expedited or inexpensive process. In addition to a high application fee for processing, they will be required to pay any and all back taxes before their application can be approved. They would not be able to nationalize for a period of 10 years after their legal status is approved.
If we structured it this way I believe 70% of the aliens would opt for the non-immigrant expedited worker visa.
I agree with your approach.
The key is, before any of this becomes politically viable, the border must be shut, hermetically sealed. Illegal immigration must be near zero before anyone would trust the government to normalize their status. But if they will do this, most people will accept this kind of solution.