This is less about my own suggestion, more a prompt to discuss boarding and salvage in general, and how it's affected by combat. Don't worry, I'm not about to talk about boarding during battles or making it a mini-game, I'm more concerned with what defines the chance for a disabled ship to be boardable or recovered. As with everything, I'm not sure how 0.8's upcoming changes will affect any of this if at all, nor their practicality or feasibilty, but to get my suggestion out of the way:
Salvage, by default, occurs if a ship is disabled but not destroyed (regardless of whether it's enemy or friendly). There are two further variables: Whether the salvaged ship is recovered intact, or has sustained damage to critical systems - producing a (D) variant (In the case of modded ships or those currently without them, simply applying the hullmods - jumping ahead, how this would work with weapon mounts I don't know).
The type of damage sustained by the ship, and how often to what systems throughout the battle will determine these variables. For example, if it suffered a lot of EMP damage, it's almost guaranteed to have fried flux systems, possibly to the point of rendering all other systems inoperable.
If it had its engines damaged heavily, it's almost guaranteed to have degraded engines, if not destroyed engines which would necessitate a tug to get it anywhere.
If a particular weapon mount were damaged repeatedly throughout a battle, it's likely to provide a malus to weapons mounted on them or disabled outright.
If it took tons of HE damage all over, it's likely to come back with compromised armour.
And so on.
Then comes the question, "What's the point of salvaging ships if they're just gonna be degraded afterwards?".
If you take care not to completely obliterate the ships you're fighting, you can take them more or less intact, though this'd be extremely rare unless you outfit your ships specifically for the purpose, but this'd come at the cost of the firepower needed to bring them down in the first place.
The next logical question is "Won't it be too easy to get new ships if it's easy enough to avoid doing too much damage?"
This is where Marines and surviving crew come in. The less overall damage the ship sustains, the more of its crew survive, meaning more Marines are needed to guarantee a successful boarding action. Surviving officers on board the ship could also give them a bonus (Depending on skills...?)
So you now have the ability to, damage dealt and marines spent notwithstanding, gain a ship (Or ideally, the option of attempting to board/recover all disabled ships) out of each battle. Where's the trade-off?
Recovery of any vessel, captured enemy or friendly, would necessitate the investment of heavy machinery and supplies to restore its basic functions, as well as time. If these are unavailable, they require a tug to tow them to a port that has the necessary facilities, or conversion of one of your operable ships into a tug with the Monofilament Cable hullmod, expending CR and supplies. If you don't have anything that can serve as a tug, it must be restored on the spot - this could be another utility for the construction rig, speeding up and possibly diminishing the costs of the process.
So, you got a crappy ship out of the battle that can't fire a Vulcan cannon without overloading. To go back to that first hypothetical question, "What's the point of salvaging ships if they're just gonna be degraded afterwards?", you'd also be able to restore these ships to their original states at certain ports - in order of cost, mostly through ones belonging to the faction the ship is from, but also through military markets you have access to and black markets. And costly it would be - each (D) hullmod you remove would cost somewhere around 1/3rd of the ship's value (Increasing the less friendly the port's faction is with the ship's originating faction, due to sourcing of parts), as well as further investment of supplies.
I think I covered the bases of cost/risk/reward, the hope would be that 95% of the potential salvages you simply disregard due to not investing into the logistical side of things, but when you encounter that one ship you really want for yourself you can take it, if you win and if you're careful about it.
And before I forget, the upcoming Salvage (Note, I wasn't referring to this when using the term "Salvage" before) mechanic, ie being able to visit the sites of past battles, could be another avenue for this, and a "career" option in its self - Invest enough into the logistics and you could go around picking up the husks from other battles, salvaging, recovering and restoring them, then selling them off. Both this and taking them as prizes from direct engagements are how I imagine the pirates getting the vast majority of their ships. There could be a couple skills in the Industry aptitude revolving around this.