The best way to give us more difficulty, is to give us the other half of the game that feels like its missing.
Make managing our colonists a far bigger issue.
Start, by dramatically reducing the birth rate, so that onwship of 12 colonists wont fill a whole base with bunny like Marsborn, having a self sustining population should be an enormous releif. Earthborn should be retiring and going back to earth, people shoulld be dying of things we didnt expect, developing enough culture and comunity to sustain children shoudnt be a matter of 'they have a bar, med station, gym and cassino, sexxy times are now'. The populations of mars should feel precarious, and losses should be felt.
Then, give us more to do and more we need them for! Populations on Mars should get more and more demanding concitions should change, from something like the Antaric reserch station, to a colonial homestead, to a frontear town, to a [potentially] thriving city. We should have to adapt to those changing needs and prepair for the future, as requrments and expectaions change.
We should be watching internal and external politics, our sponsors should do more than give us a score card. Instead think of say the first phase of Tropico 5, with the Crown making demands, your gaining favour, possibly even other sponosrs looking to let legal juristicton over the colony. Keep Mars in the public view and get more aplicants and more population (which should alwyas be a very scarce resorce), but more attention means more demands in turn. Or play quietkeep things small, enjoy relitave freedom, but reduced support.
Internally, theres a golden opertunity for some great internal tensions between Earth and Mars Born, between going with the sponsors demands, or your own needs. But that's not enough. Faction A thinks you should concentrate on getting populatin up, faction B is saying that woumenwill all strike if reduced to baby factories. Factons C and D are fighting about whether mining gains should be used by the colony, oe exported back to the home world, faction E really wants to see another sponsor take over the facualty and you need to get that dealt with without becoming so repressave your own present sponsor intervenes...
Then you have issues like what to do with criminals when all your resorces are so tightly constrained?
I mean the human element has so much potential to add this whole extra layer of depth and complexity, especialy with the 1 sol/1 year timescales, and thats what I thought we were getting because right now, it feels like the game stops right when it should just be getting started. With imediate needs adressed, and positive upkeep beating flows of all resorces theres no pressure and no reason to do anything else but sit tight and coast till you get the mystery.