chevron, the original glide slope at LCY was 7.5 deg; this was used by Dash 7 aircraft landing on a short strip within the longer runway length. The reason for this angle appears to have been entirely due to noise considerations.
The 146 certification involved a compromise from the required 6 deg approach to provide adequate clearance of Canary Warf; 5.5 deg was allowed with the use of a high quality ILS glideslope beam and/or PAPI. Noise was also an issue, as was the obstacle clearance of the proposed bridge to the East.
To my knowledge, no two-stage approach was used or considered. Previous research work by RAE used initial approaches up to 6 deg with a change to 3 deg (4.5) below 1000ft; these options were not viable at LCY when landing to the East due to the close in obstacles.
IIRC some subsequent aircraft certifications have considered a ‘two-stage’ flare to overcome weaknesses in flare performance or to alleviate a higher than normal approach speed, but generally these have not been successful as the resulting landing distance increases rapidly (unable to claim 35 ft TCA).