That's precisely what I'd like to avoid if doing respite though. I wouldn't want foster children every weekend (and wouldn't be able to due to work), and wouldn't want to be asked every week. The fact yours seems to be 'fully booked for weeks' suggests they're actually doing Foster care nearly full time, just with different children every week. Which would definitely put me (and probably others in my situation) off.
For me, I'd be able to provide respite about one weeks a month, or once every six weeks or so, with the soft bed in the office going up and the desk chair being moved out, the same as I do when I have anyone to stay. This definitely wouldn't be acceptable for a full time living situation, but for a night or two a month, yeah it would be.
I probably could support a child with complex behaviour for a couple of days, but there's also hundreds of children in foster care who don't have particularly difficult behaviour who would probably really enjoy a weekend away, who aren't able to get one because of the fact respite is prioritised for higher needs children (as their FCs quite rightly need a break), and there's a huge lacking in available respite carers.
For me this would be a good place to start recruiting younger people, which is what OP asked about in the first place.
@AmyandPhilipfan that sounds ideal to be honest, and exactly in keeping with what I've said about about a kind of 'extended foster family'. I'll have a look into the idea of extended visitors, as I hadn't come across it locally.