>>16711353 (OP)I probably wouldn't bother with micro-climates on mars. there are global duststorms that can easily carry away any atmosphere you carefully poured into the big ditch.
also mars is losing atmosphere anyways, due to the lack of a magnetosphere.
i wouldn't invest too much into gas on mars, unless you can keep it inside a surface dome, or a subsurface cave.
radiation is another big problem, also due to the lack of a magnetosphere. if you really must start in the ditch, you might want to drill into the side and put all of your humans into that tunnel.
rocks are a cheaper radiation shield than anything you would have to build.
the olympus mons thing could easily work, and be useful, if you just shoot regular rockets from there.
a railgun/spinlaunch thingy, where your payload experiences extreme aerodynamic forces due to being fast inside an atmosphere is probably a no-no.
refueling a rocket from earth with fuel from mars would be a first big step.
building a rocket with components from mars would be the next.
setting up infrastructure to transport rockets to a mountain top would be huge, but also very expensive. we haven't even figured out how to do that on earth, and i don't think it would be easier on mars.
bulky heavy cargo is typically transported by ship/barge. that's not an option for mountains, and definitely not an option for mars.
you could build a big train, but that would have the disadvantage that you need to build big tracks. and you need to maintain those. while being irradiated.
there is an amount of rockets you'd have to shoot to orbit for all of that to be worth it, and i think we're a good couple of decades away from that point.