How often do you travel with a ton of cargo? Would a roof rack with a really good cargo net help? We used to have an okay net - not big enough for the whole cargo area but it was super stretchy with lots of hooks - like a bunch of intertwined good thick bungee cords. We also did a roof carrier for years - I forget the brand although I'd know it if someone suggested a few names of course (or 2 seconds after I post this, whichever comes first - LOL!). I've seen people with Thule units for sporting equipment, but ours was much bigger than that, but fit within the roof rack space. We used it for all the stuff we didn't need quick access to during the trip, and for stuff we didn't want the kids to get into. It did get hot up there so anything temperature sensitive stayed in the car (food, etc.) but all the beach chairs and toys and towels and umbrellas and so on went up there. If someone needed something from up there, we just undid a couple of latches, swung the top up on its hinges for a foot or so, and fished out what was needed.
A few years ago I took a bunch of kids to they airport with big camping backpacks and sleeping bags and other camping equipment, and we unloaded everyone in about 5 minutes in the drop-off area. My husband and I had a good routine together for unloading the whole thing at a vacation destination - easily flipping up the entire lid and then standing on the van running boards to unload, with one grabbing and handing stuff down to the person on the ground. We also had a bike rack on the back of the van or wagon, whatever we were driving that year.
So if you aren't on the go every day, but something like every 2 weeks, a carrier might work great. We kept ours in the garage rafters in the off season and on the deck if we were going to use it again soon.
I only suggest this option because you seem so reluctant to give up the minivan for all the other travel comfort reasons.
I agree with you about a trailer - you have speed limits with that, because they swing around especially if you're in a lot of wind. You have to know what you're doing when you put the car in reverse too. I think they're the only way to go for vehicles like skidoos and snowmobiles, but for regular cargo that's not secure, you need to add in chains or bike locks and that sort of thing. An enclosed trailer gives security and protection from the elements, but obstructs visibility. An open one is the exact opposite - not secure and not weatherproof, but good visibility.