I'm convinced his original concept was this, but at some point the mandate was to make decepticons almost all airborn (Brunt and of course Megatron were the only true decepticon ground molds outside of micromasters)
my reasoning is thus
shockwave's fists fold in and have exhaust vents. Very strange for vents to be facing forward like they are in his official alt mode. But very reasonable to face back like in boombox mode
boombox mode is VERY stable and balanced. No accidental tipping
the antenna is way too small for a regular ship's communication tower, but seems just perfect for boombox mode
His grey gun makes no sense in any mode (including robot) other than this. Can't even understand the inspiration for it unless it was this. Connecting his two other weapons, but having a big fold in the middle? Terrible design. Not to mention it looks ugly.
His speaker-shaped foot coverings that form the front of his dropship mode are slanted for no reason, while in boombox mode you can rotate them to be aligned flatly with the front of the tapedeck
and tower mode has almost zero transformation-dependent molding. His forearms each have a tiny groove to align them with his back. That's it. Everything else is just his robot mode with his backpack flipped up, arms swung back, and hip rotated.
Which doesn't even make sense because that's nothing like what his communication tower looked like.
I'm betting some guy at hasbro is looking online and going "I TOLD you guys boombox was better"