I wouldnt say its always a bad thing for clickies to specialize, their smile should never disappear though.
The medieval theme does have many beautifull clickies from the 90's that can still fit multible roles. A change of helmet can turn a soldier into a captain or knight. He just can't aspire anymore to become an astronaut or businessman. Some could still be pirates though, just like some pirates can be medieval villagers.
It's just important that a good balance is kept, like knights should have the armor seperate so that it can be removed in full. Some 90's knights make surprisingly good peasants without their armor.
If a certain balance remains it still encourages creativity to assign clickies different roles within their theme. Dedicated to one theme is good, stuck with a single role in that theme is not. Well maybe aside from monks and priests.
