Here is something I started but never finished.

Advancing Warp Nacelle sub systems design
Damage to the new warp nacelle subsystems will reduce the warp drive efficiency by 33% the times the speed of light. If pressed past the efficiency one SU worth of damage to the nacelle per round.

Bussard Collector & Deuterium Collection Grid plus emergency Flush Vent
SU’s Used: 1 x size
Power: 1 power round / Emergency Flush Vent requires a 2 power to blow.
The Bussard Collector and the subsequence collection grid plus the Emergency Flush Vents all count as one in the ship.
During the late 23rd Century the Bussard collectors were removed and the Deuterium Collection Grid. The subsequence collection grid was redesigned to increase efficient. Some time in the before 24th Century the Bussard collectors were being integrated as the vessels required the starship to refuel far more often than the vessels with the full Bussard Collector.

Space Warp Control Sensor
SU’s Used: 1 per nacelle
Power: 1 power round
The Space Warp Control Sensors scan the stability of the warp field, the subspace bubble, and the subspace wake left behind the starship.

Primary and Secondary Warp Chillers & Intercooler
SU’s used: .5 x Size
Power: 1 power round per nacelles
The warp nacelles cooling system that keeps the coils at a serviceable level of use. The coils over heat the vessel fails to maintain the stable warp bubble.
The Primary and Secondary Warp Chillers & Intercooler have a minimum of 1 SU’s per nacelle.

Subspace Normalizer
SU’s used: .5 x size
Power: 1 power round per nacelles
The Subspace normalizers are installed to prevent the damage to Subspace matrix. This damage to the Subspace Normalizer will cause the collapse of the warp engines and throw the vessel violently from Faster than light speed.
The subspace normalizer is not necessarily a required part of the warp nacelles. The normalizer was not installed in Federation starships until the mid 22nd century.
The Subspace Normalizer has a mininum of 1 SU’s per nacelle.

Let Me know what you think. It was something I was playing around with a few years back.