I think updating the models in trem would be a very good idea.
It wouldn't be very hard,
get somebody to draw a reference image for each of them,
model them in a somewhat middle range poly count,
texture them, rig then convert the animations to vertex keys.
However getting that into trem and having it work is something I don't know nor understand.
I feel like it's a rather simple project minus getting them into trem that would add a lot of life into the game.
The current UV maps/textures look like pixel art,
I feel like we could keep the aliens the same looking while adding more detail,
have more polys, better textures and have some massive improvement.
Because it would be a visual mod the client would be effected,
and other than better looking models it would otherwise operate the same.
If it's not "that hard'
I seriously think we should start a visual mod for this.
I can model, rig, UV unwrap and animate(very well) in Blender well.
I can't draw references,
code or draw up UV Maps though.