I'd need to know more about the coop before I could make any kind of judgement on whether it was suitable for alpaca housing. In terms of safety of housing alpacas where chickens once lived, I don't see any problems.
Is this just the covered area and they will have access to a paddock as well? Or are you thinking of locking them in the chicken coop at night and then moving them elsewhere during the day?
It would be used as a shelter and they would have constant access to a paddock. I'm just trying to see if I could even get alpacas or if it will always be a dream. My parents say that we don't have enough room for alpacas, but I measured and we do have enough unused land for 2- 3 alpacas.
Good for you! Over the years I have lived with Alpacas, I can tell you that they are highly social animals and don't do well alone. You may have to get another one soon for Job to be comfortable.