West Properties had originally wanted to build a 24-storey residential tower at the heart of the three-block development on the Princess Street car park site - part of a key conservation area next to the city's famous canal.
However, following extensive pre-planning consultation, fears were raised both by local residents and by English Heritage over the size and impact of the proposed development.
As a result, Simpson, who was chosen from a shortlist of five to mastermind the project a year ago, has now dropped the height of the main glass tower by 28m to 15 storeys. This apartment building will sit next to a 13-storey hotel and a new seven-storey office block on the 0.5ha plot, 70 per cent of which will be given over to public space.
Francis Hilton, West Properties' land acquisition and planning director, said: 'Simpson rather felt he had given a lot of thought to the historic element so [these demands] came as a big blow.
'We thought we had come up with a very adept solution to the site, knitting modern architecture into the cultural surroundings.'
He added: 'In terms of the impact on the scheme, we have had to re-look at the cost plans and how to deliver the project while maintaining the quality of the buildings and the integrity of the open spaces.'
A planning application is due to be submitted by the end of the month and, if approved, the project could start on site in June next year.