First off, doing such a moving experiment with only your own funds is a lot harder than if you had billions to millions of dollars to do it.
Secondly, people won't be trapped inside on Mars and will make regular, if not daily trips outside on EVAs (we may need a new acronym as there's no "Vehicle" here.)
Thirdly, a lot of hardware will be outside the "container" including the power generation from nuclear power or solar energy. (Likely nuclear powered sterling engines that have already been demonstrated in subscale versions.) (This contributes to the difference in funds point on my first point.)
Fourth, even though you didn't mention it, I'll add it here to preempt a counter argument. The radiation risks are overstated. Radiation on Mars is at least half that of being in space because you have radiation from one half of the "sky" blocked by the planet itself. Also while the radiation levels are certainly elevated, they're likely not going to kill you. Any long term colonies are going to be mostly underground anyway. (Or more likely simply buried by shoveling dirt on top.)