*WARNING: LONG POST*
As for blink drive, basically I was thinking that you would need more than the current 100% of FTL efficiency to blink effectively. With lower efficiencies, blinking would get some sort of penalty - what exactly depends on how blink works.
Low Efficiency Penalties: The core concept I have for blink/ftl is that once blink is initiated, the ship dissapears instantly (in hyperspace or some such) and a "wormhole exit" (or "ship ghost"?) appears at the blink/ftl target position. After some period of time, influenced by distance, the blinking ship would come out of the exit. FTL efficiency would heavily influence how long the ship spends in "hyperspace", so while ships with only a few FTL drives could still blink/ftl, it would take forever and any enemy could easily anticipate and avoid the blink. A ship designed for blinking could enter and exit blink/ftl before an enemy could react, probably depending on range.
Adding "wormhole exits" for non-blink FTL would make a lot of sense for single-player/campaign too, once enemies are able to FTL around the map.
To initiate blink, maybe ships could just have their FTL drives charged like how it currently works. Or maybe the FTL drive consumes power at a fixed (variable based on efficiency?) rate, and slowly builds progress towards being ready for an FTL jump, with the time needed based on the overall ship size vs # of powered FTL drives (and FTL efficiency?). Maybe ships can initiate blink instantly with any orientation and velocity, or maybe they need to slow down/stop first (max speed based on FTL efficiency?).
Once blink is ready, maybe the ship would blink immediately, or maybe the player can choose when to initiate it (and the FTL drives should continue draining power while waiting, or else you could hold onto a blink forever). Maybe the wormhole exit would be invincible, or maybe not and killing the exit pulls the real ship out of hyperspace (wormhole health influenced by FTL efficiency?) Maybe the wormhole exit would be fixed grid-relative, or maybe it would be fixed ship-relative, or maybe it would even be fixed enemy-relative.
Maybe ships would need to set a blink target before they start charging, or maybe you don't have to set a target until the FTLs are already charged. Maybe there are limits on range (determined by FTL efficiency?), or maybe you
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The general idea behind low efficiency penalties is that both long-range FTL and short-range blink would be affected equally by low FTL efficiency, but the penalties would only matter in combat. For example, who cares if I spend 10 or 15 seconds in warp space (with a wormhole exit visible) if I'm blinking out of space-dock? But 10 or 15 seconds makes my blink nearly useless in combat. Similarly, it's no big deal if a freighter spends time charging FTL on a trade run. But a battleship fleeing from a fight will take heavy damage if it's FTL drives take too long to spin up.
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Assorted notes: There could also be a direct penalty, such as energy drain from all parts (in addition to shields). Higher FTL efficiency would reduce or remove the energy drain.
It's also fairly realistic if a ship with many FTL drives has quicker FTL travel than a ship with few FTL drives, in addition to it's effects on blinking.
It would be interesting if sensors could reveal additional or more detailed information about FTL/blink or "wormhole exits".
IMO blink/FTL ramming should definitely be a thing, mostly because it's such a huge science fiction trope (but also because it would be incredibly frustrating if ships could block FTL/blink). I have a few ideas on how to prevent this from being OP.
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Determining FTL Efficiency: In the above section, I talked a lot about "low FTL efficiency." But right now, it's relatively easy to build ships with near 100% FTL efficiency, which would still allow nearly every ship access to a combat-ready blink drive. When blink drives are added, IMO FTL drives should be changed so that ships that currently have 100% efficiency would only have 50%, or lower - but reduce FTL fuel costs in bounty hunter (or boost FTL fuel drops) so that fuel usage is unchanged. This is effectively the same thing as allowing ships to have more than 100% FTL efficiency.
The overall effect of this would mean that ships could operate FTLs effectively and cheaply with low efficiencies (e.g. 50%), but their FTL jumps would take a while and their blinks would be basically useless in combat. Only ships that build specifically for ultra-high FTL efficiencies would be able to effectively use blink in combat. A side effect of this would be that ships designed for rapid FTL travel (e.g. a VIP courier) would also be able to use blinks in combat, but IMO that makes sense and is not an issue.
On a related note, I think it would make a lot of sense to have more interesting FTL efficiency design choices. Right now FTL efficiency is circular around each FTL drive and cannot stack to buff range, so the only effective strategy for FTL efficiency is to space out FTL drives evenly around the middle of your ship. But in science fiction universes (e.g. Star Trek), efficient FTL travel demands specific ship geometries.
IMO it would be a great change if there were more options for FTL coverage area shapes, such as long and thin areas, arcs, areas far away from the FTL drive, sharply defined shapes, or similar. The weirder shapes would have more coverage or efficiency per $, but would be a lot tricker to use. For example, you could build a stargate that projects an FTL field into empty space so that other ships can fly in and jump away. It would also be interesting if adjacent or nearby FTL's (either the drive or the coverage area, or both) could interact - boosting or interfering with each other to alter a ship's overall FTL efficiency.
I'm not certain what the best way is to implement more FTL shapes. Maybe put an option on each FTL drive allowing players to choose which shape they want. Or maybe add more FTL drives, each with their own unique shape.
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TLDR: anybody with an FTL drive can blink, but useful in-combat blinking requires a lot more FTL drives than useful out-of-combat FTL.