You should make it metal and then have them guess at each level where the stairs are increasing the amount of c4. The anti-raid pillars on the outside can still be wood if resources are an issue. Though I would put metal bars on the top just in case if someone trys to use the jump glitch and gets in by luck. Good design for such low resources and would be able to be hidden in rocks pretty well as well.
For a 5 foundation base its pretty awesome! As I said I use it all the time :)
Edited:
Mine is for sure better for a start. It require just 3 foundation in a row. Of course it is better to think ahead and have spare place all around for more foundation and pilar. Not sure if it's good because I'm not sure if pilar defend againts ladder correctly.
Than you need to go up with more story. More story you have more hard it is to raid.
So one of the 3 foundation is for the stair, one stair at one point. You need to alternate the stairs.
But dude. a 5 foundation base that requires 4C4 to get to the loot room. Its a starter base. I just showed the bigger one as an example as to what you could do with it once you gather more resources. Its just my opinion, and I don't doubt yours, but mine requires less resources as a starter base, that is necessary.
Edited:
Im 99% sure you can attach a foundation to that taller base even with the scattered pillared foundations around it.
I tried it. You can't.