Basically, a single problem with PvP right now is that it punishes you a lot for losing.
This can mean lots of score loss if you lose in PvP2 against a "noob" because you're running a fun dragon rainbow while your opponent is running a shrieker rush deck. Or maybe you want to test a deck for PvP and so play a deck in PvP since that's the only way to do so, and lose a lot since you're still balancing it. Now I'm willing to take this loss, simply because it's so much fun, but others aren't.
Hence, PvP3*: Sandbox PvP. It would be upped/unupped, and would not affect your score in any way, winning or losing. To not make it another form of all rare farms, you could either make no spins or make it the same cost/reward as T50 to punish people a small amount for losing.
*When I said this, I meant it in the light that it is the 3rd PvP option, not that that's what it would be called. Sandbox or Unranked would be the correct term.