Is there a site for searching fares (esp. flights, but trains and stuff cool too!) when EVERYTHING about your trip is fuzzy, from when you'll travel to how long you'll be there to what cities you are going to in a large radius?

I'm asking due to travel within the continental US, if that helps, but would be cool to have this for international!

Often when I'm searching for flights to visit family on Google or Rome2Rio or something I can be "fuzzy" about an aspect like searching a few days around a proposed departure or arrival date, or looking at a pricing matrix for trips to/from a given set of airports.

But usually my travel is much more flexible, and I'd to search based on that. I'm more likely to be saying: "At some point this Spring I would like to visit my family in Utah and Arizona. For the Utah family I would love to fly to their small regional airport so would like to know the price there, but am also open to flying to a further regional airport, or to the larger major airports in SLC or Vegas and driving since that's usually cheaper. For the Arizona family it would be great to fly to Tucson, but Phoenix would also do. I also don't care if I visit Utah or Arizona first, so swapping the airports there would be something I want to know the prices on, too. And, it'd be most ideal if I could also see the difference in flying from Tucson to the regional airports or Vegas, and from the regional airports or Vegas to Tucson, to join the two legs of the trip. And I'm flexible on the length of each leg and length of entire trip."

Even without being able to check that "mid-trip connection" going between Arizona and Utah, just having the other things would be nice. I'm envisioning something where I can select "these are all the airports I'm willing to use; I want to be there at some point between X date and Y date but the actual timing and length of the trip does not matter" and be shown a matrix or variety of options so I can weigh things like cost vs. distance airport is from family (and thus need to rent a car or ask for a ride, etc.).

Does such a tool exist, or is this too complicated? I've tried Rome To Rio and Google, but I haven't found a way to incorporate this much flexibility to see so many options. PanFlights seemed more flexible, but even with putting in lots of flexibility, it keeps saying no flights are found despite my knowing options do exist under my selections.