Yeah, thinking about this a bit more, shouldn't stomach proteases break the protein sources into dipeptides? I found a few comments online arguing that hydrolyzing doesn't matter and may cost more. If that's true, then we should only care about the protein types of whey, especially the alpha-lactalbumin content (higher tryptophan). I think bromelain would only help people with reduced protease production, and it likely won't break apart hydrolyzed protein any further. Of course, theory requires a test, but I won't add bromelain to my hydrolyzed whey test.
Bromelain cant harm though, is cheap, hydrolization is certainly not perfect, and it has other positive effects on body such as anti inflammatory, pain reduction etc.
Adding bromelain to mix might help.