I would guess that anything is possible. After all, they are able to have vinyl with the fiberglass coves and steps outside the pool walls. I would think it would be the same (if anyone makes them) to have a larger, very shallow "cove".
That said, I recall reading a few posts about people with tanning ledges that wished they did not have them and instead had more room in the pool. Kids will not be on the ledge for long and floating on a chair in the pool gives the same tanning ability. Also I imagine that keeping the ledge clean could be work as well since most cleaners will not get on them.