Going to be honest, that stat block is a mess, and if I were your DM you'd be getting a hard no from me.
The chances of us getting our preferred homebrew content done is very low, that's not to say that we will never get any homebrew content, after all, we currently have a whole homebrew ranger subclass, but I wouldn't bet money on your favourite homebrew being put in.
I don't think that 5e even has a mechanism for using weapons in four arms, though would not surprise me if that is just me being ignorant.
Older editions had specific mechanics for getting additional attacks with more arms, but that was also when you got many extra attacks from other sources. In 5e, extra attack is actually quite rare, and it isn't given out by racial stat blocks. Look at
Thri-kreen for an example of how four armed races work in 5e.