Heh... I do not care enough to allow nay-sayers to bother me.
I will respect the opinions and perspectives of others, but no person can talk me out of my own opinion and perspective, that all Greased Lightning stacks had need of was a serious and functional fix, not to be given up on and delete Greased Lightning into a damn trait. Verily, it is more probable that Monk will not turn course back around, that I both acknowledge and admit, but I came up with my redesign before 5.4, any way; and have just put it on a shelf, since then.
Aaaaaaany waaaay, copy and paste time...
First: Greased Lightning stacks only affect “speed”, or in other words, they only reduce WeaponSkill cast time and recast time, spell cast time and recast time, and auto-attack delay; where-in each Greased lightning stack reduces these by 5% per stack, up to four stacks and 20% reduction.
(I can comprehend why the Dev Team chose to remove damage increase from Greased Lightning, and chose to stay with that.)
The only way to gain a Greased Lightning stack, is to enter Raptor form, and shift forms from there, Raptor to Coeurl to Opo Opo, unto which the third action, being Demolish, Rock Breaker, or Snap Punch, will activate a Greased Lightning stack, when the Monk shifts form again, Opo Opo to Raptor.
Greased Lightning stack duration has also been given a increase, up to a maximum of 60 seconds, and while the Monk flows through form shifts and the rotation, each Opo Opo-to-Raptor form shift of a third action, which activates and maintains/upkeeps Greased Lightning, will neither grant the full Greased Lightning stack duration, nor refresh the duration to the full duration.
Instead, the first Opo Opo-to-Raptor form shift activates one Greased Lightning stack with only 10 seconds on the Greased Lightning stack duration.
Every Opo Opo-to-Raptor form shift after the first, will activate another Greased Lightning stack, up to the maximum of four, and extend the duration of Greased Lightning stacks by only 10 seconds, up to the new maximum duration of 60 seconds.
I chose to design Greased Lightning in this manner, because I think that it would be "better" than if it were brain-dead level of almost not possible to NOT upkeep and maintain, as seen with Warriors' Storm's Eye, Shinobi Huton, or Dark Knights’ DarkSide.
Also, keep in mind that even at a (super) slow 2.5 GCD, that would be 7.5 seconds to gain 10 seconds, so as long as the Monk keeps their rotation in flow, it would be easy enough to build up to, and stay at, the new maximum duration, while to build up to that new maximum would be "essential", for Greased Lightning stacks to not be lost when ever the Monk can not attack targets and maintain them.
Side-note I: Just a personal perspective... If 10 seconds per 1-2-3 rotation is still "too easy", it could even be just 7, 8, or 9 seconds, to make the stack maintenance, and to reach the maximum duration, a little more difficult.
Side-note II: I think that it would also be ideal if the fourth Greased Lightning stack has no restriction to and/or lock behind any action, which was Fists of Wind in the past, and only have a level-lock, like the second and third Greased Lightning stacks; while the Monk will unlock the fourth Greased Lightning stack at a much lower level than waaaaay up at Lv76.
Since Greased Lightning II was, and still is, unlocked at Lv20, and Greased Lightning III was, and still is, unlocked at Lv40, I chose to follow the pattern, and the Monk will now unlock Greased Lightning IV at Lv60, instead of Lv76.
Addition: A idea(not my own idea), that is worth mention.
If the duration of Greased Lightning runs out, just one stack of Greased Lightning is lost, rather than all stacks of Greased Lightning are lost.
My own thought on this: after the one Greased Lightning stack is lost, the duration of the Greased Lightning stack/s that remain/s, defaults back up to 10 seconds, so that the Monk has a chance to recover the one loss, before the Monk faces another loss.
Keep in mind that the maximum duration is now 60 seconds, so to even lose the first Greased Lightning stack, under the assumption that the Monk had proper maintenance, would take up to a full minute of the Monk doing naught at all, to happen.