I think it would be quite interesting to have a strength and fitness system, swayed if you lug around muffalo or lift some weights. The benifits being increased melee damage, faster movement when carrying heavy objects and a happier colonist.
You could also make it a necessity by having various strengths of gravational force for each planet, for example if you came from a planet with a higher gravational force and moved to a lower one doing the same amount of work and exercise your muscles would slowly but surely waste away.