I'm still hoping/waiting for a devlog about maps. But they'll have to finish creating the areas before making maps of them...
And I understand Atchodas's concerns.
It's the same for most quests - if you get stuck for one reason or another or stop playing for a while and then return, NPCs won't have anything to say to you while you're working on their quests. I imagine it can be really jarring in some cases. Right now there's only your notes. If you could just ask what you were supposed to do again, that would be an improvement.
One of the reasons i would prefer directions ( painted on walls or just simple road signs )
There are road signs and wall labels where they make sense, meaning that they won't point to long-abandoned complexes like the battery recycling plant, only inhabited areas like Camp Hathor.
is the "gating" for TNT charges really a must ?
Yes, absolutely. If the player could travel everywhere (it's not just the caves, you can get everywhere
through lower underrail's tunnels with some TNT) before the south railroad tunnel is cleared, it would cause a number of bugs and probably even break down the game's narrative structure. Also, the early game up to Depot A seems to be meticulously balanced for the content you can reach before returning the drill parts.