Those hooks/loops are referred to as ISOFIX or "LATCH" and are federally mandated on new cars, so you should probably be able to get the regulations about where they're allowed to be located and what gauge the rod is, etc, and figure out the best way to attach them.
I'll let you in on my plan there, though...I actually plan, while my son is in a car seat, to just use the 2pt lap belt. Of my 4 cars, only 1 is new enough to have the LATCH. My daily driver, a 99 Camry has 3 pts in the rear, and I have to use this annoying seatbelt "clamp" to basically turn them into a non-retracting 2 pt. Every car seat we've owned had "How to install in an older car." It's easier to do it with a 2 pt adjustable than a 3 pt retractable.
The reality is that you have to get it TIGHT AS H-E-1-1, because there is no attachment point at the top of the seat.
So instead of installing Latch in my car, I"m just gonna use the stock 66 rear belts for his seat...I know I can get it REALLY darn tight, and the seat will be in fairly well.
That said, obviously a LATCH system would be better and maybe safer...but I don't trust my ability to install the loops any more securely than the stock seat belts are by stock. HMM. I wonder if you could use the snap hook style eye bolts, threaded into the stock locations, and use those?
http://www.summitracing.com/parts/GFR-109L/ Something like that? Maybe not.
As far as your "Even with the hooks child seats are hard to install" let me do a little advocating here...When our son was somewhere between 12 and 18 months, my wife and I were at Target, and they were selling Britax brand child seats for like 220 bucks. She said we HAD to get one, and they are normally way over 300 bucks. I scoffed at the price and said there was no way I was spending that much money on a car seat. I think any married guy can see where that went...So we go home with the car seat, and I start installing it...
It was SUCH a good design. MUCH better than the other seats we had. The installation was a snap, and the way it was designed left me feeling better about it...lots of steel parts instead of plastic.
Instead of hooks with snap-back metal tabs on it, it has a buckle type bracket with a release button. Instead of one long belt that goes from one side of the seat, through the seat body, to the other side of the seat, each side has it's own dedicated adjustable belt, and the adjustment is as easy as yanking on the belt. So to install it you loosen the belts, snap each belt directly onto the LATCH points (which is way easier than using a hook, because you can push the Britax buckle end right down onto the loop, instead of having to hook behind it) and then you push your knee down into the seat, yank on the two belt ends, and that sucker is in there tighter than a drum. It takes 3-5 minutes to install one instead of 10-15 it would take me to install his old car seat, and feel GOOD about how it was installed.
I HATE when you spend a lot of money on a product and the result is really no better than a cheaper one...but in this case I feel every penny was well spent.