I have thought about a few things since i saw
and about Mark Wahlberg's character Cade Yeager from there. there seems to be a plot hole towards the end when he's using the transformer gun sword and using some military tactics while fighting Lockdown. the way he holds the gun and the way he moves looks as if he is trained. many say its plot hole in the story but what if it isn't. This is just a thought it has been many years since the cross over comics and things like that i myself is from the original G-1 transformers generation and G.I. Joes from the 80's, and the comics clearly show the G.I Joe and Transformers share the same universe.
So here is my theory Cade Yeager is potentially a retired G.I Joe and the Joe i am thinking he could be is Mainframe now (Dataframe in the re release of the joe toys) for a couple good reasons. Cade claims to have left high school at the age of 17, Mainframe's bio card says he graduated from high school at age 17. Cade is an "inventor" who knows how to hack computers such in the case of him hacking the drone that Harold Attinger's (Kelsey Grammer) men used when they attack Cade's home in Texas. Mainframe was a computer specialist for the Joe team and always found ways to use technology to their advantage. Mainframe was from Arizona not to far away from Texas. Cade mentions that his wife died but what if she didn't die but perhaps she was killed by cobra where it left him so devastated that he retired from the military and moved to Texas to raise his daughter? Mainframe is quoted in the series that his wife left him after he returned from Vietnam its a similar scenario. And Main is also quoted to have children in the series due to some lines he says while in Transylvania and he says it remind him of taking his children trick or treating.
The clincher that Cade is potential Mainframe is this, Cade repairs Optimus Prime in Age of Extinction, in the cross over comics of transformers vs G.I. Joe it is stated that Mainframe aided in the repairs of a critically damaged Bubble Bee. no needs to believe I am right this is just a thought and a theory. Mark Walberg is in talks to return as Cade in the next Film as well as Lenix, who could also be part of the Joe team, and there are many many mentions and hidden hints that G.I Joe is in the background in the Transformer movies. Again this is a theory not fact nor proven, and feel free to comment your thoughts. and as reminder there is another piece of evidence that G.I. Joe and Transformers are the same universe there is an episode in the third season of G-1 Transformers name only human where an older Cobra Commander makes an appearance.