If the developer is willing to work with you to agree a proposal that goes some way towards meeting your requirements as well as theirs, that should carry some weight with the planners, although they must also be guided by their policies, hence my original suggestion of asking them for an opinion of the site. Any degree of dialogue and compromise is better than the alternative. My derelict school site is the result of the owner, the parish council and the planners being unable to agree on any proposed development. The roof caved in two winters ago and with all the windows and doors now missing and trees taking over the site, it's only a matter of time before the walls start to crumble. It's opposite the main entrance to our lovely parish church at the heart of our village.