Paul,
All the extra "movement" is a cummulative thing which includes the booster. If you remove all the RHD brake conversion parts, it reduces the weight of the car by around 14.5kg as well.
What you lose in the pedal pressure assistance from the booster, you need to make up with an improved pedal leverage ratio to make the pressure acceptable. You also need to replace the pedal lever arm with one that's at least 8mm thick (or more) as the arm itself flexes. Bracing the pedal box also braces the firewall.
The remote reservoirs are not a requirement, they are installed here for other reasons not related to this issue.
The fact is, a careful choice of street pads (ones that work best on cold brakes) will have the factory components working adequately for the job. However if one expects these same brakes to do the job on the track, well, they haven't experienced seriuously good brakes.
The question regarding the legal compliance is simply answered by a Blue Plate certification from a qualified mechanical engineer that the system is up to the job. (Goes for any modification within reason actually.)