I love the challenge mode idea! I better start thinking a few.
* All maps have no walls! Inspired by your debug post.
* All main complex maps (Materials, Factory, Research, Access) have only one exit. And that exit is always at the most opposite side of the map!
* You must enter the Garrison before taking the stairs...
* All weapons are explosives, for those not getting enough of it.
* All enemies are Behemoths! Now I'm really getting out of hand...
* More recyclers per floor! And their propulsions are upgraded to flight units! Raise the next bar of annoyance!! Yeahhh!!!
* Boss enemy per floor, guarding each of the stairs (extra powerful Sentry?). Must be destroyed before proceeding.
I know they're all off-the-wall crazy stuff, but I'm sure they can be fun!
* Every time you are spotted, a squad is dispatched
* No items from enemies (reverse of Scavenger)
Very thematic! The "no items from enemies" can also be thought of "dropped items from enemies are fried up immediately". Pair this one with Scavenger mode and you'll end up with *almost* nudist mode.EDIT:
* Bigger map size, possibly 2x bigger or more.
* Programmers are dispatched more frequently. (Food clock ticks faster)EDIT 2:
* A side-story about a war between your ally robots and enemies. The tile where you enter the map becomes an entry point for your allies to continuously spawn and attack. Hostile robots will also continuously spawn and attack as well, but toward the direction of the entry point. (Similar to how enemies spawn and attack in the Warlord map) Enemies will continually grow stronger over time, and if they manage to reach the entry point, it will be sealed and will no longer produce ally robots anymore (in other word, you're screwed).EDIT 3:
* No inventory challenge! (perhaps no storage unit as well!) Good-bye indestructible backpack with unlimited mass support!
* Every terminal contains an operator (perhaps also nerfing the chance of assimilating trojan and hackware drop)Feel the pain of endless reinforcements!EDIT 4:
* No hacking at any machine! (Or if that's too restrictive, then separate it into "No hacking at terminals" and "No hacking at non-terminals")
* All exits leading to the next floor are sealed off (unless that's the only kind of exit left)a.k.a. You must go through branch exits whenever possible!
* You only gain 1 evolution point whenever you evolve.