Let me preface by saying I'm not a Monk main, just an observer with a general idea of how Monk functions.

I know that during 4.x, it is/was a slight DPS increase to use Tornado Kick at the end of Riddle of Fire, then Perfect Balance to regain the lost GL. If Perfect Balance is indeed being increased to 120s with the release of Shadowbringers, then TK will see even less use outside of SE's intention for it: to burn GL stacks for damage when downtime is inevitable. This is assuming that Anatman is fixed to not require at least one GL stack to use (which would further cripple TK if unchanged).

Perhaps SE should embrace using RoF and TK together and actually build it into RoF itself via one of the following options:
  • Option 1: Tornado Kick's cooldown is increased to be slightly longer than Riddle of Fire's duration. Tornado Kick gains an additional trait that removes its GL consumption during Riddle of Fire.
  • Option 2: Riddle of Fire grants an additional buff with the same duration as Riddle of Fire (let's call it "Lightning Focus"). Lightning Focus is consumed when using Tornado Kick in lieu of GL stacks (making that Tornado Kick "free").
Either of these options would make Tornado Kick safe and free to use during every Riddle of Fire window, giving it more utility than just being a pre-downtime tool. Monk also lost a few oGCD abilties, so this could fill the gap a bit (at least during the damage buff window).

I personally prefer option 2, as it doesn't affect TK's cooldown and can also be expanded upon (e.g., granting more than one "stack" of Lightning Focus when activating Riddle of Fire).