UK Designs - Priority Practice Change

The UK IPO announced at the most recent RPWG meeting that it is considering changing its practice to permit filing a declaration that the design is identical to a claimed priority filing, so as to avoid the need to file a certified priority document. Sounds sensible enough, but are substantive and procedural differences worldwide so great that a similar form would have a dissimilar effect and vice versa? And is it right that third parties should be unable to look at the priority document?
Comments welcomed, either here or to me.