Having a phobia of raw fabric edges is a useful thing usually, but with pleather, you're usually all right for surface applique type things (IMO) since it won't fray and is also thick enough for the glue to not show through. (if the backing is white or some other color that might show on the edge, you can always carefully sharpie the offending color on the edge so that it doesn't.)

As for foamies, I haven't perfected the art (although when I get home I'll be attempting to for KOS-MOS...), but from what I've heard/seen, a flexible gesso (liquitex stuff is usually bendable) with a flexible paint on top might have good results. as long as your sealant and paint are able to move, I'd think it'd be all right. (it's not like it'll get bent a ton with the vinyl probably being rather stiff underneath of it too, I'd think)