It might be a nice thing to have! But it might not be too necessary --- maybe a logic analyser telling you the program counter could do most of the work?
I say that of course without ever having tried it. If you can get your hands on one for cheap, you should probably do it :-D
For AppleNet, one thing that would be loads of help would be to understand better what the stream encoder/decoder PAL (part no. 341-0180) is up to. My wild guess is that it converts regular bits and bytes to some kind of encoded version for the network, but I don't have any basis for saying so. If anyone wants to take a crack at it, the JED file is
here on Bitsavers...