Indeed Mutants are fucking useless for role-play, anytime I try doing something remotely role-play related I just get fucking killed on sight, it says for them to build underground? Where exactly is underground and you can't fucking build shit in them tunnels. I've also played on servers with crab-people and jeez they're fucking amazing, they'll serve a much better purpose then fucking mutants who have no choice to kill people because they've got nothing to-do, they don't have no set purpose.
This new addition if it's possible of course would open a whole new realm of possibilities how ever I do see a problem with it, someone could potentially farm crabs like Michael said the longest surviving crab turns into the crab queen people could exploit this then get their friend to kill them and they split the money. Some positives like mentioned before would hopefully be a bigger increase in role-play and interaction with others a new exciting job that could create lots of fun for everyone.
I believe that they should spawn with knifes or fists perhaps you know to act as their pincers so that they are able to protect themselves but however they shouldn't be allowed to be killed on sight like the mutants only if there's a valid reason for them to be killed I.E killing/hurting someone. They obviously shouldn't be allowed to attack people for no reason as well.
Conclusion;
I conclude that this will be a great overall addition that will bring much more enjoyable moments to the server that should increase role-play along with interactivity with other players.