I'm hooked! Can't wait to see the final version. Is this leading to something you plan to release on Steam? (No pun intended)
As for suggestions.........
Some kind of storyline, perhaps. Or a storyline/free play option. Maybe the odd survivor you could recruit. More enemy variety.
An occasional event where you have to fight off an attack while you're docked, either at the warehouse or the trader, would shave some of the monotony. Which may be rewarded with discounts or a rare or otherwise unobtainable item from whatever trader you defended. And the possibility of being attacked while searching a warehouse would add some tension. A wider variety of items to loot and more locations to scout, like factories, towns or cities, each having their own different loot types, with a few junk items thrown in for that element of chance with useless stops vs prime loot stashes. Maybe food, water and medicinal items for your character(s). Toxic or radioactive zones that require limited use environmental gear or upgrades. And an odd point now and again where you have to choose between lines to travel.
I know that's a lot, but you did ask for suggestions.
Anyways, love the game. Love to see where it leads.