Why does Bruce bother working out if he can just use biohacks? He has the know-how and is a scientist. Heck, Slade doesn't need to, after his serum injection.

He would probably see it as cheating or cheap

Bruce has Bane's Venom and Lazarus to enhanced himself in the past though he worries about the addictive aspects.

That's his pride getting in the way. Why play fair? It's that or being put out of commission/long-term crippling.

Like those are his only options... The dude's a scientist, concoct a formula.

Yeah his counterpart Owlman created a drug which enhanced his brain and used cybernetic suit but he does became a bit too reliant on them, Bruce isn't willing to go that far.