Spot on with that Bulldog. I'm with you on using Bull blood like that. I'm not averse to it, but there are often better options out there. To give an example, there's a lad with a nice stamp of bulldog and some other lads with good working dogs have approached him to use the dog for stud, for better strength of jaw, head size etc etc...you know the craic. But they'd be better served, as you say, going to the lad who has a similar sort, but carries the attributes they are after.
As for earth dogs, well there's so many different breeds contained within many of the established types already.