Rams don't care any more about pH than any other fish unless breeding is a concern, and would not bother the corys, but still, it will make even shorter work of shrimp than the gouramis.
I'm racking my brain and it would seem peaceful blue tropicals are few. neons and cardinals have blue, though I don't know how many midwater schoolers you would want to shove in there.
The only other fish I can think of would be a betta, since they are tailored to come in just about every colour including blue. One male would work just fine in your setup, or even several females might be a neat idea.