Better Car Seats

For the start of the ideas series, go here.

We used to have a mini-SUV but when we got pregnant with our third, we had to upgrade to a mini-van.  The van is fine, though it is often too big for simple parking or for mileage concerns.  But we had to go bigger, our car seats mandated it.
Those with small children know what I'm talking about so let me explain it for everyone else. 

• When kids are very young (less than a year old) you can put them in a seat much like a basket.  You strap them in and then carry the basket out to the car.  This basket locks into a plastic base which is strapped in tightly.  
• The next step up is the more traditional car seat.  It's a full seat that is strapped in place.  It has a full back that extends up to the head and arm rests. 
• After a certain age (or weight gain) they go to a booster which is a much smaller piece that rests on the car seat and raises them to a height where the regular seat belt can be used.

Here's what you need to know, the first two items there are so large that you can only fit two of them into a regular back seat.  Even if you could fit three adults, there is only room for two infants.  So if you have a third, you need another row of seats.  And voila, you have a mini-van.
The solution is simple, though as far as I know, it's not offered on the market.  For the early 'basket' seats, someone should offer a double base.  The baskets would simply sit right next to each other, leaving space next to them for someone to sit.  The car seats would be similar.  Instead of individual seats, a double should be offered. 
All of the seats would be designed to work with all modern safety protocols, of course.  The seats could be offset a little forward and back to make more room.  We're simply talking about changing the shape of molded plastic, so there shouldn't be any technological leaps here.
I don't know how big the market is but I'm sure it's there.  We hit the limit with our third child which isn't that large of a family.  This approach would make sense for any family with twins.  Maybe there would even be a market for triplets or quadruplets. 
In any case, it doesn't make sense that you should need an entire back seat for two infants or toddlers.  There simply must be a better way.