Mongoose could probably do a print-on-demand or PDF with 15mm scale deckplans for the larger ships and we'd still buy them... they'd be more useful than the micro-scale deckplans we have now.
The way I see it, unless a GM intends for a PC group to actually board one of the larger ships, all we need in a book is just an outline of the ship - possibly a side and front elevation and external plan - the stats are the main thing. That way we could only buy in those deckplans we intended to use in-game and PCs wouldn't know the internal layout of a ship just because they happened to pick up the book... of course, you may want to let an ex-navy character's player pick up the blueprints, at least for a while...
Then again, I'm also the kind of GM that doesn't like to catch players reading the wrong books at the gaming table... or even away from it if they can't separate in-game and out-of-game knowledge. I've been known to use my favourite punishment, which I call "Doubling Up" for reading the wrong book at one of my games... Basically I don't allow my players to read any book they couldn't know about in-character and also discourage idle browsing mid-game, since it distracts players. It also depends on
who it is too - our pet rules lawyer usually got quaranteened from as many books as physically possible - he can't argue about what he doesn't know exists.
Basically, when I had to pick a random member of the party, I used to roll the next-highest dice for that group - so 5 members, I'd use a d6... doubling up meant that the extra pip got used for whoever had earned one of those punishments. This isn't actually as severe as it sounds since I never use instant-death traps, but it got the players to behave. Incidently, I also used the reverse - doubling up was also used in good encounters for those players/characters who'd really tried to help the group and the scenario and for good roleplaying.
I strongly recommend it as a way to control disruptive players. Incidently, our rules lawyer and our resident power-gamer were the two most doubled-up players in our various games.
I'd also like to lay my hands on 15mm deckplans for some of the player-likely ships out there - I've done the Beowulf class and the S-class on Coreldraw and scaled those up to both 15mm and 28mm just to see how big they are (both pretty basic deckplans, but perfectly functional) but it'd be nice to have more available. They'd be useful for those scenarios that take place on the PCs ship and involve a little combat or needing to know where everyone is standing at any given time.