It is possible to write and compile commands using the SCI Studio script compiler (although there are still a few problems with the code generation...), but the biggest problem is that in SCI, the script resources script.989 - script.999 contain many predefined classes (such as ego) and script.255 contains the dialog and control classes, and until someone rewrites those resources it willl be virtually impossible to "seriously" create a game in SCI...
However, if someone does rewrite those resources correctly, creating an SCI game should become quite simple :-)