That's assuming you know with 100% certainty how they'll design the game. People had theories about going into the past with WoTG before released and were pleasantly surprised how "streamlined" the "mobs appearing in the present under certain conditions being met" played out.

You can still give bonuses for going through dungeons with speed, they simply just have to take it Nyzul or Salvage style rather than gauntlet style which a lot of people says is archaic anyway.