It is possible to sand the scratches but this isn't easy by any means. You can sand the light scratches but deep ones will be impossible.
If the owner wants perfect doors then the owner has to provide you with perfect doors. I have gone through this many times; it's not the painters fault for the delivery of damaged doors, period! The biggest problem is it is almost impossible to find all scratches before staining, no matter how hard you try.
I think #2 will work the best with a little sanding for light scratches. Watch out after doing the sanding. This will close off the grain and make it difficult to stain. Rub the sanded area with acetone to reopen the wood pores.