In either direction, your second IR, or a ridealong PPL (61.75 in FAAland) are pretty much the only major shortcuts, and maybe reduced training hours. The exam and test standards are what they are.
Personally I have *only* done CPL exams both sides of the Atlantic and the FAA IR written, as I've nothing in my game plan that wants an ATPL. CPL/IR is fine. I dodged the IR(R) written, and am dodging the EASA IR writtens - first for having an EASA CPL, and second for having an FAA IR and over 50hrs PiC IFR. Not exactly a shortcut, but equally I'm grateful for the exams I've not had to do.
G