PS4 Package Research, today PlayStation 4 developer @Tustin made available PKG Merge which as the name implies aims to combine PlayStation 4 PKG file parts joining them into a whole PKG file.
Download: pkg-merge-master.zip / GIT
Here are some details on the PS4 Package Merge tool from his recent Tweets via Twitter:
I made a tool that merges PS4 PKG parts into one whole pkg file in golang (@RedEyeX32 wanted this)
prob works for more than 1 part but i didnt test em yet
To quote from Tustin on NGU on the PKG Merge PS4 tool's origin:
"Well, by default when you download packages from Sony, they are already in 4gb parts.
That's why Red wanted the tool made I suppose."