The scheme in Wellington Street - officially called the Westpoint project - is a joint venture between developers KW Linfoot and Scarborough Developments and features a 52-storey residential skyscraper next to a 29-storey block and winter garden (Simpson in line for tallest tower in Leeds).
Yoo has been involved with the scheme from the outset, but now Leeds-based Brewster Bye has been appointed to produce all technical drawings relating to the internal layout of the development.
Simpson told the AJ that he was glad to have side-stepped the internal layout design package as it allowed him to concentrate on 'architecture rather than wallpaper'.
He said: 'I am happy - interiors change all the time. I am not demeaning the internal design process, but I have to concentrate on creating a fantastic building for the city.'
KW Linfoot development director Richard Dean said: 'It was always our intention that Ian would take care of matters up to planning and then concentrate on the building's shell with another company taking care of working drawings.'
Simpson added that he expected work to start on site in June, with completion scheduled for late 2010.