Good idea. This is what I would propose.
[1] First all must register name, address, and employer plus foreign address
[2] All would be put on a list to be considered legal immigrants in the order that they registered
[3] Create retroactive number of immigrants to be allowed in
[4] those then legal given a time to become citizens
[5] those found that did not register would be deported.
[6] those electing not to become citizens would return to their homeland.
[7]DNA data bank