Are you really trying to say Law doesn't have to sustain his Room? The fact of the matter is, if you're starting Luffy off at his very possible best condition, then you have to do the same with Law; if you start Luffy off with the best thing he can activate already activated, then Law starts off with the best thing he can activate already activated. Otherwise, it's bias and an advantage towards Luffy.
Launching Doflamingo across Dressrosa has nothing to do with speed, but with power. Throughout the entire fight, Doffy made numerous notes about what G4 increased, and each time it was power. Not once was there any mention about an increase in speed.
Doflamingo's reaction to G4 speed and G2 speed are nearly identical. Doffy was able to dodge both Gear 2 and 4, leaving an afterimage and getting a short distance away.
You must be registered for see links
You must be registered for see links
Doffy was also unable to react to G4 and G2 until they were both mere inches from him
You must be registered for see links
You must be registered for see links
And we know he reacted to the G4 in that panel because he applied Haki to his face in the next page to try and block it.
Edit: Links were broken, here are the images uses
You must be registered for see links