Well, FWIW, I did consider an X-Com spinoff RPG, back when TFTD was new and I had no programming experience at all.
The basic ideas, as far as I remember them:
-Entirely separate continuity, with aliens refluffed to match
-Sandbox-y, with randomly generated locations and events; never got around to deciding whether there should be a pre-written main plot, or a set of victory conditions
-Interface would have been fundamentally similar to the original, but with a number of more or less obvious changes (such as a dialogue system in the battlescape)