Multiple "z-levels" (actually just teleports):
Definitely a huge problem with Ice Colony is the stalemates, draws, and grinding halts that ladders and elevators bring. If either side is guarding one of the ladders, then that ladder is almost effectively impossible to breach for Marines. Xenos can have a bit better chance due to Queens and screeches, but it isn't favourable and it isn't fun to do, plus it requires a Queen to de-ovi - which isn't really possible at all times.
To fix this, there's two ways I foresee: Merging the map to be one "z-level", allowing the underground section to be an extension of the top area would alleviate this problem greatly. It would allow for more marines to be able to breach an area, or xenos, without having to wait for timers to complete.
Secondly, ladders can be turned into staircases with seamless transitions. I believe one of the developers was already working on this. I personally believe this to be the inferior choice, as stairs are a bit awkward in their use on any server I've seen, and from what I've seen in gifs that the devs have put out as examples.
Snow:
Snow punishes both sides, and it doesn't add anything to have it be so punishing. Xenos can clear it a bit easier, but it's still tedious to do so. Getting stuck in snow is awful, and the fact that it's random doesn't help any better. When you walk into sticky resin, you know what's going to happen. You'll be consistently slowed unless you clear it with your tools available. Snow is the opposite. You might be randomly stopped, unable to move. You might not. It's not really consistent. The slowdown is painful.
To fix this, I would make snow have a slight, consistent speed debuff ONLY. No getting stuck in snow. That sucks, and isn't really fun. The other thing to make it less unfun would to make it easier to clear. For xenos, just one action instead of several to go from thick to no snow. For marines, having flares clear snow slowly due to heat, flamers working better, shovels doing it faster, really all these are needed.
Unused map:
In my mind, Big Red is the anti-thesis in this regard. It's map is used almost all round consistently, with viro being slightly problematic due to it's location. Ice, on the other hand, really only has a few key spots that are used. LZ1 -> T-Comms/Bar, Engineering (and really only once), Dorms, Excavation, Hangar sometimes for deployments, same with Dorms. Hydro, Warehouse, Mining Outpost, Admin, Garage, Medbay - these really aren't used whatsoever, unless a xeno runs in there to juke marines. Underground is a bit better in this regard, given that aliens consistently fight in all of it, to a certain degree.
I can't really give a fix besides overhauling the map, so this'll be all I put.