Aside from his betting issues, he has twice been caught on video being insulting to Brentford. I'm not sure that paints a picture of a great character.
And beyond that, while he's a very good player, he isn't an elite striker and at his age isn't going to suddenly turn into one. His general play is good, but his goal returns for Brentford have been heavily inflated by penalties and minutes.
At the price I assume we'd have to pay for him (Brentford reportedly have a £60m asking price), I'd be surprised if there weren't better options elsewhere for the rotation striker role we have available. Be it cheaper or with greater potential than Toney possesses.