Okay so here is my idea. We mine out a tunnel from the already existing excavation, and make it fairly long, and as well as an area or something to hold a stand at or something, considering that looking at the map, its hard to herd/trap such a wide area for enemies to come up, while if we made a controlled corridor, we pretty much know about it at all times. Plus we could produce proper stone doors, and corridors with flame traps and the like. Or at least, we should move our workshops to a different location away from the entry point.
That's a lot of digging. I was hoping that in a first phase, we'd limit access to our work and living areas by putting up a few walls and making a few breakthroughs. Such as on the map below.
In green: 4 new walls to build
In red: 2 new tunnels to dig
That should seal off all entrances except perhaps the demon gate and the frog room pit.
What's lacking with that plan is a way to get in or out of the safe complex. I'm not sure where to put the entrance, really. Suggestions?
My own idea: inside our complex, we have a trapdoor that goes a level below our current rooms. From there, a tunnel runs parallel to the river (so we can flood it if we wish), The tunnel forks, with one exit leading to the cave area, while the other connects to the frog room stairs. Would require a lot of digging, too. If we go with that, we might need a temporary entrance with a door or two.