In general, liquid yeast shouldn't be used without making a starter to get the cell count up (and the second generation will have thicker walls). Yeast vials are notorious for having low cell counts. If I lived in an area where yeast is hard to come by, I would exclusively use dry yeast.
The reality is that all ale yeast is Saccharomyces cerevisiae (lager yeast is a different species but the same genus). What else is Saccharomyces cerevisiae? bread yeast. I'm not saying that you should use leavening yeast to ferment your beer but if you reserved some wort from a pale ale and added some baking yeast, washed the yeast and did it again, by the third or fourth generation, you'd have something very similar to American Ale yeast. You could do a little experimenting to see what happens.