119.5
About the drugs bit.. this act covers drugs too.
There is provision in the RTA for 'Special Circumstances' on driving while having had too much to drink. This act is based on the RTA therefore, it's logical to assume that the same thing would apply. However, it's not been tested, yet.
Tiredness is a point, but even a small amount of drink will have a more pronounced effect on a tired person. Therefore rather than prove the BAC limits are too low, you may be reinforcing the reasons for them being low.
Your list of other professions, I can't see how a lawyer will do anyone serious damage when having a BAC concentration as low as this act, maybe there is a case for some other professions to do so, some already have one. (eg train drivers).