Deportations are subject to appeals to and review by immigration courts. The court system is jammed with overload.  Special court systems in the U.S. are vulnerable to dysfunction by surges in cases,

Trump will likely cancel DACA, Parole and TPS. Much easier to do. Republican senators will use this to force an immigration bill in importance with those in the 1960s and 1980s.

A good comparision with the mass deportation idea is JFK’s plan to install bomb shelters across the country in 1961. The plan blew up and he dropped it quickly.