So I was thinking seat and aisle should have lots of storage, but affect function. If a seat has much of anything in it (more then 5 vol?) you shouldn’t be able to use control while in that square directly (aka sit and drive). Now for aisles (which currently don’t have storage) I think they should have lots of storage. But if you pile things up in them they should at first slow you down when passing and then become impassible when near or at full. Simple stuff, but it makes sense. 
stuff in an aisle would slash about in motion. while things falling to the ground through the aisle is silly, it’ll take some thinking to make something like this workable.
100 volume for seat storage is quite a bit.
My DeathRoller has like 4 guns and a few hundreds rounds of ammo under that seat, a few hats and I think something else.
That is way more than what I can put under my IRL vehicle, so it’s already taken into account that it could be in a pocket behind/side etc.
There’s coding issues where you need to assign the object to a vehicle (storage tag) or to the ground.
Your seeing storage as all neat and tucked away. I’m seeing the 650 and 1000 trunk/cargo storage and it’s not so much that is it’s like this ‘magic’ storage underneath. It’s some shelves/cabinet/crates like my dad had filling his electrical van. Stuff was in shelves, and boxes etc. Which is the reason it is ‘slow’ to move though. The area is FILLED with stuff all over crammed together so it doesn’t move.
It is odd that they fall to the ground, but I don’t have issues with it because I have 1 aisle with lights next to my bed in any vehicle and that is it. Everything else is cargo etc. I just don’t craft over that square.
Same thing happens if your storage spot fills up. Once you know what is going on it’s not that much of an issue, it even tells you it is full.
One option is for them to code it loose like you want, and when you hit the brakes they can apply the form of the electromagnetic pull bionic (but code it for anything not in storage) and have a few hundred objects strike you in the back of the head, the windshield and bust everything up. But that isn’t very fun either.
Maybe not Fun but it would be funny. Your stuff is telling you “Build storage next time dummy!”