An option in the server config to allow activating Flamigo when it haven't fully recharged yet (but duration is reduced based from recharge progress).
And allow deactivating Flamigo while still in swimming mid air state (Suggesting key to be sneak+sprint or double tap jump)

[items.helium_flamingo]
#The amount of time (in ticks) after finish flying with the helium flamingo until a player can fly with it again.
#Set to 0 requires a player to wait for helium flamingo to fully recharge.
#Range: > 0
after_flight_cooldown = 0
#The amount of time (in ticks) a player needs to fly using helium flamingo before a player can stop flying manually
#Set to 0 requires a player to touch the ground, enter the water or run out of flight time to stop flying
#Range: > 0
flight_cancel_cooldown = 0