I like the general idea, but it has to be done so we still don't have full consequence free control of all immigration. I reckon our dwarves would become quite upset if their spouse/children/close relative/friends weren't allowed inside the fortress and sent away due to having a according to the management unnecessary skillset. Much FUN could be had by this if the player were too strict on the immigration and the dwarves decided to revolt and get rid of said immigration officer, who would in their eyes be the one to blame. Or maybe your legendary weaponsmith would decide to pack his bags and leave as well if you failed to consider that the cheesemaker you just sent back to the hills was his nephew or something similar ^^
As long as there is a way to keep track of that, otherwise it would be really hard to find out who's related to who and such. Maybe when a batch of immigrants arrive, the immigration officer heads out into the designated area or whatever (which could be inside your fortress in a well-protected area if you wanted, rather than outside your front door) and then brings up a screen like the trade screen. There you will see all the immigrants in this particular batch and various assessments of their skills and problems and merits and such, along with any relations they have with your Dwarves in the fortress e.g. "cousin of Bomrek Nethdastot, Expedition Leader".
The quality of this screen depends on the skill of the officer, like the stocks screen depends on the bookkeeper's skill. From this screen you can sort out which immigrants you want to take in and which immigrants you don't want to have, but if you turn away Dwarves with close relationships with your Dwarves e.g. lover, best friend, then your Dwarves could become unhappy and complain to the mayor or whatever. If, however, you allow in a Dwarf who is a mortal enemy of one of your other Dwarves, then your Dwarf will get upset also. The screen could just be two columns - Dwarves you want to take on (right side), Dwarves you want to leave (left side). All the Dwarves start off on the left and you manually move them onto the right with your arrow keys if you want to take them.
The area for the immigrants could just be a gathering-place where they sort of mill around, like a zone. It could even be a designated zone like "meeting hall". When the immigration officer reaches that zone the screen appears.