Not sure what to call this, but I'll try and explain what I would like to be able to do the best I can.

I made some quick parts to illustrate what I'm trying to do.

Let's say I have part 1, a rectangular box part.

When I create my assembly, I want to kind of "link" them together, the actual part has bolt holes and places to bolt up to, in this example I'm going to pretend it's getting bolted together:

The additional section is an "add on" section and you are allowed to have several if you would like. By default there is also another section that bolts on to the end, that is different than the others.

It will always bolt on to the end in to the same spots regardless of how many pieces there are or what piece is there.

So, my question is basically: Is there a way to set up an assembly so that I can still work on it without it being really bogged down, and be able to switch between having several extra sections or none if necessary?