I think that one reason for the empire underperforming in comparison to RebelScum might be that they draw from a thinner pool of uogrades. Rebels have Astromech Units for themself. Scum has Illicit and Salvaged Astromechs (mostly) for themself. RebelScum has a lot of Crew updates that are relatively popular while the Empire doesn't etc.
So how could we introduce Empire specific Upgrades that could be used by a large number of existing Imperial ships?
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Title: Standardized Modifications
Restrictions: TIE only, Empire only, Limited
Ruels: You may equip another Title.
You may equip an additional Modification Upgrade with a TIE only restriction.
You may not equip several identical Modification Upgrades.
Cost: 0
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Long story short Every TIE could get an additional modification which would be limited to these who are TIE only. At the Moment this would be
TIE-MK II
https://vignette1.wikia.nocookie.net/xwing-miniatures/images/5/51/Twin-ion-engine-mk2-1-.png/revision/latest?cb=20150706162622
and
Lightweight Frame
https://vignette1.wikia.nocookie.net/xwing-miniatures/images/c/cb/Swx63-lightweight-frame.png/revision/latest?cb=20161205173613
So nothing too broken out of the box imho. Punishers and Bombers would be able to take LwF to boost their defence without giving up GC or LRTC for example.
This would open design space for something that is basically a TIE-specific Upgrade.
Examples for new usefull TIE-only Modifications could be
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TIE-Turboloader
TIE-only, small ship only
Your Action Bar gains Boost
Cost:2
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A cheaper version of the engine upgrade Large ships get more mobility out of boosts so I think cost2 is justified for a small ship version. This would enable the TIE Advanced and Defender to get a boost and take vector thrusters which may be bad news for TLT spam.
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Standardized Ordnance
TIE only
All your Rocket Torpedo and Bomb Upgrades cost 0 Points
Cost: 7 (maybe +/- 2 I am not sure)
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Not sure how balanced this is but the Idea is that the cost effectiveness of ordnance goes down the more you take. Alpha Strike lists that want to spam as many Rockets or Torpedos as possible in the first engagement aren't pushed with this cause it is too expensive. But Fully armed Bombers and Punishers that have several options for different threats would become viable.
Is this Idea useful or just a mess? What TIE-only Modifications would you like to see?