It's more than a 4-dimensional space - it's a probability distribution over 4-dimensional space, one that you want to explore ahead of time, and you never really know for sure where you're on it until your trip is over. I'm yet to see a planning tool that handles this.
What I mean by the "probability distribution" part is, your trip plan isn't really a specific plan - it's a set of possible plans. You may have concerns like, "what if we arrive late on the first day?", or "what if the main attraction for the 2nd day is closed", or "we're not sure at this point where we'll eat", or "oh crap, it's raining today, what do we do?", etc. You have to navigate these questions in your head. I'd love to have a tool that makes this easier.
What I mean by the "probability distribution" part is, your trip plan isn't really a specific plan - it's a set of possible plans. You may have concerns like, "what if we arrive late on the first day?", or "what if the main attraction for the 2nd day is closed", or "we're not sure at this point where we'll eat", or "oh crap, it's raining today, what do we do?", etc. You have to navigate these questions in your head. I'd love to have a tool that makes this easier.