Well the concept of those bases is pretty nice, maybe in the future we can get some rope-ladders.
Negative point would be you need another person inside to let it down for you to come in or if you are playing alone everyone could use the rope-ladder until you pull it back when back at base.
No, it would come with a mobile phone.
You call your house and it will drop a rope for you :) 
Can't build anymore foundations near that, i don't think, that space in the rocks can only fit 1 1x1 foundation
but that middle pillar with his box on it will decay eventually
That depends...
Some time you can put the fundation a little far away from the house, but then make it higher than the house and you can jump a lot even if you lose most health. They did this on a server I was playing, and jumped from one house to the other even though you lose health.
Keep Cool