IB are not interested in trailing stops for business reasons - and their reasons make sense - though its hard to know if the practical issues would be as serious as the theortetical ones -but, if i owned a brokerage - i would not allow trailing stops
a stop is only the "stop" the trader envisioned, if it gets activated at or near the desired level - otherwise, once activated, it is a time bomb sitting there waiting to be filled at an unknown level, with each succesive and different fill - forcing the market lower and lower - and it is a way to potentially bankrupt individuals and brokers - if everyone had a stop one point below the last market high - and the markets started to drop - where would the resulting market order be activated!