I'm going to break with the mold here and suggest the perfect lore handwave for the battlefields -- disruptor missiles. Upon detonation, these create a field which inhibits travel drives. These would be assumed to be a part of every ship's arsenal, but due to the amount of interference they produce, any given fleet can only maintain a single disruptor missile ready to launch at any given time, and it takes several hours to prepare another for launch -- if a fleet attempted to maintain several disruptor missiles it would disrupt its own travel drives enough that it couldn't manoeuvre with anything other than reaction thrusters, giving them a practical maximum acceleration of 3-5
g or so (not nearly enough for practical manoeuvring within the game's context and only viable in fan fiction and theatrics).
Anyway, the idea is that when fleets move to engage, one fleet or the other (or both) launches its disruptor missile, which creates a "dead spot" in space that lasts for hours. At the scales on the strategic map it's easy as sin to avoid these areas, but on the tactical map it's another story -- and why once a pursuer launches their disruptor at your fleet, they wind up disabling their own drives as well as yours, until of course you can manage to get out of range of the initial impact point.
To help cover the "well, if we save our missile, we can just launch ours at the enemy after we manage to get out of range in order to disrupt them while we escape" scenario (q.v. Independence War 2, where launching an LD missile was a viable escape tactic), it's not difficult at all to justify that launching a disruptor missile also disrupts all other ready disruptor missiles in the area -- so that even if another fleet kept its disruptor missile in reserve, it would be knocked offline by the detonation of the first missile launched in the conflict. The existence of these disruptor missiles also explains away why you can't use "interstellar scale" missiles, since these missiles could easily be intercepted by disruptor missiles anyway (as "close enough" rather than "direct hit" actually counts in their regard, giving a vastly unfair favour to the disruptor missile).
When fleets meet head on, the launched disruptor missile is instead detonated in between the fleets in order to reduce the likelihood that they can alter their manoeuvres, and prevent any "sudden" moves on the part of the enemy. Only fighters and light frigates are manoeuvrable enough (and small enough) to avoid the initial disruption effect and attempt flanking manoeuvres -- larger ships are stopped dead on the initial detonation, forcing them to reinforce from the side they came in from.
The final piece of the puzzle is the simplest: that disruptor missiles are a dime a dozen as the technology is ultimately extremely simple, and that the disruption they produce isn't some fantastic ultra-high energy radiation source, but simply more akin to a puff of chaff or some such. Each of the little "chafflets" is simply an electronic jammer that disrupts drives nearby -- once it burns out, natural travel speeds can resume. (Heck, this can even be used to explain what the "space dust" is in every battlefield.) The initial "burn" is the strongest, knocking travel drives (and other jammers) offline all around. Those jammers that survive the initial burn then persist in maintaining a disrupted area until their power cells finally go and/or the chaff disperses enough that it no longer has enough strength to maintain a dead spot. Therefore all ships simply have disruptor missiles abstracted in their Supplies.
As for the name, well... The problem with games that feature "dropping out of warp" is that in reality, "combat" speed is "as fast as you can go" and "travel" speed is "as efficiently as you can go" --
e.g., an Iowa class battleship would travel at its cruising speed of 15 knots for best range, but jump to flank speed of 32 knots if it detected a threat. With "warp" style gameplay, this logic is reversed -- you can go very very fast and then all of a sudden for reasons inexplicable you have to reduce your speed in order to be able to fight? Why would you not attempt to capitalise on your enhanced mobility and make use of your extreme speed to launch long-range missiles that will come screaming in at ridiculous velocities?
Based on that, I think anything that emphasises speed might be irrelevant -- making it more likely for me to lean towards "travel drive" as the best option. But if we want to change the name to represent the
technology rather than the
semantic/conceptual purpose of it, I might lean towards "
tensor drive".
Now on to boarding... to be honest, I don't see why boarding should be more expensive than buying ships. I think the cost should
approach that of buying a new ship, but if the entire universe is all about "making do with what you've got", then boarding seems like it'd be *the* way to obtain "new" ships, not something to be discouraged. I don't like the gamey restriction of one per conflict either -- if you specialise in boarding, you should be more than capable of boarding multiple vessels in an enemy fleet, but of course you're going to suffer a lot of losses and would have needed to sink considerable assets into boarding.
That's what pirates do, and it's self-balancing -- instead of focusing on the combat aspects, they focus on the boarding aspects. That makes them ruthless against lowly freighters, but easy prey for combat fleets.