I spent a good number of years designing and engineering seats. I, personally, would work on a seat with air bags inside. The smallest amount of static electricity, or sometimes the moisture from your hands, can set off one of the bags. I have seen the results, and it ain't pretty.
If you source seats from a junkyard, be sure they are the same year as the car. Otherwise, the car may not recognize the air bags, and set an error code. Of course, lots of people drive around with permanent error codes and check engine lights displayed, but it isn't a good idea.
A lightweight seat cover shouldn't impede the air bags. They are very strong, and they will just tear the fabric apart.
Police Crown Vics had special severe use seats, after a while. The earlier versions did not, and they failed, both the trim and the structure, so quickly that police departments threatened not to buy any more Crown Vics. GM cars never had this problem, as their seats, in cop cars, were already strong enough.
One of the things I liked about my 2007 BMW was that the seats, and the entire interior, looked like new after 200,000+ miles and 10 years. My Mark VIII seats were sagging, and the leather cracking and delaminating after less than 100,000 miles and 5 years.
