I feel like there is some confusion as to what PBR actually is. As I have mentioned and 3D-Store has pointed out, you can have tileable PBR textures on your model. In fact, anything that you are able to do with old-style texture maps, you can do with PBR, only better. I think some people are thinking that Substance Designer source files or Substance Painter are the only way to do PBR, but that isn't actually true. Substance Designer and Painter are just two universal standards for creating PBR textures from scratch in a procedural manner, but PBR texture maps can be created using many other methods and are no different in many ways to how "old style" texture maps worked with your model. The difference is merely that PBR textures contain more accurate data information about the surface material and how light should interact with the model. That's all. You can convert any of your older style texture maps into PBR textures automatically using certain software and they will work just fine in most cases with all modern render engines.
You don't need to unwrap or UV your model in any special way to use PBR textures. Yes, it is true that if you are creating PBR using the Substance methods (which are the industry standard now) then you will likely need a UV unwrapped model with non-overlapping islands to get the best results. However, that is not the only way to create PBR textures. In fact, you can easily convert all your older models to contain PBR compatible textures automatically now with certain software and you don't need to change anything specific about the way they are mapped.
So, in the end, there really is no reason to not use PBR for any model that is more than just a 3d print. If you have a model that contains textures, you are much better off to create maps that can be used in PBR. For example, color information that does not contain shadows or highlights in it (albedo), specular or glossy maps, metalness maps (if there is any metallic areas of the model), a normal map instead of just a bump map, a heightmap for displacement (optional), a roughness map (just the inverse of a glossy map), and if you really want to a AO map is also handy and can be created with any model that has height data. That's all you need to at least get started with being PBR ready. If the user needs more than that, it's very simple to generate new maps based on those basic PBR standards.