But it should be legal. The tests are a joke and some high profile fighters are obviously on PEDs and they pass tests. The best tests there are (the new WBC AVDA testing, UFC SUADA testing and Olympic testing for cycling) manage to probably limit the amount and the kind of PEDs athletes can take so in that sense thy succeed but they surely don't prevent PEDs
The quality of your PED is exactly proportional to the amount of money thrown at it.
Boxing is already fucking gimped by giving the star fighter advantages with the reffing (look at the beating a losing British prospect is allowed to take before a stoppage is rendered against them, compared to the amount of damage a visitor has to take), the judging (e.g.... like, every weekend), & the weight (most prospects feast on much smaller guys, to provide footage for the highlight reel).
I am not comfortable with giving the "B" side of the bill an even bigger disadvantage, in that their drugs will be coming from online Zimbabwean pharmacies & will mostly be caffeine pills & aspirin, whilst the "A" side of the bill will logically—with the removal of the limits currently imposed by the current, admittedly inadequate testing regimes—be on NASA-grade shit that turns you into a raging Hulkzilla, capable of breaking cars across one's torso & shitting sparks.
For your idea to work, boxing would need to be a reasonably level playing field in the first place, rather than the laughably diseased, corrupt & mad weasel-bastard bastion of outlaw dog-eat-dog capitalism that it is.
Here on Earth One, it's a fucking stupid proposition. Sorry. You might as well ask "Well, why bother with weight divisions if certain fighters can get away with gaming them?"
The answer—if you care about the sporting aspect at all—is not to throw up one's hands & abolish weight divisions just 'cos some connected guys game the weight, but actually enforce standards so that people can't get away with it.
& here in Britain at least, that won't happen until someone busts positive after inflicting some horrific life-changing injury on their opponent.