To get anything near as good as the originals you'd have to render out new backgrounds and have access to the prophouses. This requires Photoshop and several 3D programs.
For new actions like sligs and scrabs using doors you'd need to make new sprite frames that gel with the originals, and alter the code to enable it.
All this originally took OWI... three years?
__________________
| (• ◡•)| (❍ᴥ❍ʋ)
|