@Gazebo If I have a specialist and no remaining happiness, get rid of the specialist (so reduce by one urbanisation), but as a consequence of not working that specialist unhappiness from needs increase by 1, does that mean I am not able to put the specialist back? Or does the limit on number of specialists take in account the unhappiness reduction from working the specialist?
In that very specific case, removing the specialist and incurring the penalty would limit your ability to put the specialist back, yes.
There is also an 'end of turn' check that fires for every city and 'validates' your specialists. If your city has urbanization unhappiness and has a negative happiness delta, it strips the specialist(s) out until you are out of non-free specialists or your city is happiness neutral.
G