There seem to be two ways to look at this:
1) what do I need for the range of images I want to take?
2) what is the least I could take, if things were really minimal?
The first seems to lead to a few lenses (gee what if there is a long shot? or a wide?) and its hard to say no to the work flow and the options. Everything is treasured, and cutting is hard.
The second is useful when traveling: you talk to the gear, and make it behave - and tell "its either minimal or you aren't coming". If we can do this with our families, we ought to be able to do it to a bunch of stuff that doesn't talk back.
Seen this way, one lens, one back, a few batteries, hyper focal, a small tripod… and a few bits… might work. Or something along those lines. Remember the days with one camera, one lens?