Hard mode is senseless with this exponential growth in HP and DMG. My ship is able to take out all waves without my help and no boss survives for more than 3 seconds. That's not what I understand as "hard". Slightly disappointing after reaching lvl 50. Perhaps I pushed my gear too early with the crystal crafts?
At the moment easily possible with Ram, Boss and Bad Boy. Healing is not needed. Just launch 2 UAVs and concentrate on the vehicles and helicopters. When the train comes, only shoot its 3 weapons.
Even for a 200 bed hotel, you need no more than two elevator lines. Just build one only 5 floors and then another beneath it shifted for the next 5 floors and so on.