fkv
That node/line/area/relation distinction is somehow obsolete, because multipolygons are are relations but considered as areas. There's simply no other way than to map this shop as a relation. The only question is what relation type to use. A multipolygon won't work, because it doesn't allow for overlapping members. A cluster relation (I'm the proposal author) is inadequate, because it's only one shop, not a group of individual shops. That leaves us with a site relation as the last resort. You can't add a shop node to that site relation, because it isn't a "part of the site. e.g. buildings, parking entrances, power generators", as defined by the type=site proposal, but rather a simplified (generalized) alternative to the whole relation. A node could be a "label" member at best, but as such it shouldn't have a shop=* tag.
There are 2 reasons why site relations are not rendered. First of all, the proposal was confusing for a long time. Many mappers used it in different ways. Meanwhile the proposal has been cleaned up, but existing data may still be a mess, or at least the people responsible for rendering think it is. The other reason is that they are simply too lazy to implement a rendering method for site and cluster relations. Anyway, that's not our fault as mappers, and I don't see why we should waste our precious time discussing this when we have no permission to implement it, while those who have are too lazy. People who want to get it rendered should torture them, not us.