Don't write Eubank Jr. off. He's still got a lot of talent and has physical gifts that others in that division do not have. What he's missing is proper direction. He should look for a top trainer, one that he can respect and listen to, and take it from there. That will mean pretty much telling his father to go kick rocks.
He fought arrogantly against Groves. Leading with left hooks, not setting up any of his shots and totally abandoning his jab. A proper corner and a gameplan would have done him well in the fight.
Your post is straight from Fantasyland.
Physical talent (Eubank's strong & fit & has a good chin), yes.
Boxing talent? He has no jab, he can't throw punches properly (to generate any power he has to hurl himself clean off his feet, because he has no punch technique), little head movement, his footwork is beyond awful, he cannot cut off a ring, he cannot jab, he cannot deal with a jab, he has no boxing brain (he literally did not posit one response to Groves' solid jabbing, he didn't try to time a counter with a right over the top, he didn't try to go to Groves' body, he didn't try to out-maneouvre his man, he just swiped from way out of range & hoped to get lucky), his vaunted, displayed-against-stiffs power isn't all that ("average" hitter Badou Jack hurt Groves much more seriously) ... Even inside, Groves got the better of it & landed the better cleaner punches, when Eubank wasn't hitting legally (on the break, holding with one hand & hitting with the other or clear rabbit punches).
Yeah, he's a physical talent. Boxing history is littered with physical talents, who went nowhere & got nowhere. He got where he is by virtue of his name & that afforded him hype & a very easy ride.
What your positing is a lifetime's fucking work, not something that six months in a tight camp is going to sort out. To do what you're suggesting (combine that athletic talent with some boxing basics), you don't need a new trainer, you need a fuckin' time machine to go back to when he's like seven years old & start him all over again. & possibly a baseball bat to hit his old man with every single time he opens his mouth.
He lost ten rounds against a guy that basically fucked up & fought below par—Groves abandoned the jab for long stretches 'cos he thought one of those rights would land on the button & Eubank would go; GG has form here & it's cost him before.
Eubank is at the same level as every fit guy with no basics has ever been. It'll be enough to overwhelm domestic level fighters whose mediocre skills cannot compensate for their massively inferior physical capacity (which is why, FYI, they're domestic-level), washed-up superior fighters & smaller guys (not to mention the litany of scrubs, tomato cans & Latvian binmen his record is littered with). Anyone who can box to a superior international level will do the same to him.
You talk as if he's a well-schooled guy who occasionally drops his guard after a certain move or exposes himself via an inappropriate tactical choice—fine-tuning. He does not need fine-tuning, he needs the entire wiring loom ripped out, a new engine, a totally different suspension system, different size wheels & tyres, a different transmission & whole new chassis, with different bodywork, too!
Good day, sir.