VARiable

In that specific situation you almost feel like the hypothetical orange card for a sin bin could work like so:

• orange, yellow = off
• yellow, orange = sin bin
• orange, orange = sin bin
• and a third orange is always a red

This way referees who worry about being blamed for "ruining the game" with an early double yellow might punish players/teams where they'd otherwise find any excuse to avoid the second yellow.

This really would allow for more inconsistent decisions but it would facilitate punishing behaviours that ought to be punished but which routinely go unpunished.

The rules ("Laws" I know) keep getting written to be more objective, but the pursuit of objectivity is foolish when a lot of the decisions are always going to be subjective. Increasing the level of subjective discretion could actually make refs feel empowered to make calls they're otherwise hesitant to make because everything is so binary and clashes with the human element. Or it might not, but the situation now definitely needs fixing somehow... all that can go wrong is a different wrong.