A 190-room hotel, 350 flats and a residential care home could all form part of the proposed package to redevelop the former Syngenta site at Fernhurst.
The Comer Group, which bought the site in September, outlined the plans, which also include 15 new homes, to Fernhurst Parish Council last week.
The developers are confident that the site, which will be known as Fernhurst Park, will generate employment and address the need for residential care in the area.
But Fernhurst Parish Council has given a mixed response to the plans, which could see the size of the parish increase by 50 per cent.
Although members have yet to formulate a formal response, the plans were discussed at the parish council meeting.
Parish council chairman Carla Barnes said: "It will have the most enormous effect, but at the moment there is no planning application, so it is the only ground plans we can study.
"The hotel and residential home seem fine, and it will be good to have underground parking but I'm not convinced about the 15 family homes, which seem a bit large for the site. I can't see it being accepted by the planning committee, as in my experience, they rarely give permission to build new houses in these types of areas."
The proposals also include a small number of penthouse apartments which would be on the top floor of the conference centre known as the Pagoda building. Longfield, currently let to small business users, would remain as it.
A number of facilities would be introduced for occupants of Fernhurst Park including a health club with swimming pool, sauna, and spa pools.
Occupants of the 90 flats would have access to landscaped grounds, sub-tropical hothouse gardens, and communal dining rooms and lounges.
Mrs Barnes is satisfied that the views of the parish council will be taken on board throughout the development process, explaining that some environmental concerns raised by council members have already been addressed by the Comer Group.
"At this stage, we don't want to be too negative because we want to maintain a strong negotiating position with the developers later on. Things could be a lot worse, so we are grateful for that."
The site was originally the home of ICI, and its various successors occupied the site from 1946 to December, 2001.
Referring to its previous use, Mrs Barnes added: "This will of course have a great impact upon the village, but local people do remember when the site was used by ICI and you had 800 people working there every day, all using cars, so it's not as if we're not used to a lot of activity there."
There is expected to be a public display of the proposals at the Syngenta site in a few weeks' time when the Comer Group is expected to submit a formal planning application to Chichester District Council.