So there have been a number of threads talking about this. I know that some (myself included) have suggested that the higher tier silos have two attach points so you could chain them together. I'd still like to see that but it's not what my suggestion is about.
The deeper into my lair that I go and the more silos that I have the more I realize how much running around it takes to get stuff to my machines. My suggestion is to have the higher tier silos that are multi level have an access point on each level that they touch. No change in size or functionality or anything. Just allow me to get stuff out of it on different levels.