EU's kind of shown that astro's are placed all over on ships... Roaming about freely on ships like Amidalas, or even having fixed sockets "outboard" on big ships like that as well.
To me, none of these ship's designs imply that they're building into anything else really... The Jedi Fighter, when you look at it, really doesn't look like anything (A-Wing's been said in the past, but beyond it being red I don't see this similarity), and the new Jedi Fighter's really not like anything else besides it maybe having SOME similarity to the old Jedi Fighter... "improvement" for the war there is practical so I can link those two, but I can't link the Jedi Fighters to anything in the modern era really.
The ARC-170's design is just out there... Beyond its basic shape of an elongated hull with 2 wings that can split for maneuverability/stability, I can't say this is a ship that I look at and think "X-Wing" at all. XW and this don't even look like they'd be in the same role/category given that the ARC's are bigger/bulkier, have a rear gunner... I'd say it's maybe closer in relationship to the Y-Wing, but it doesn't resemble that fighter at all either, but if you run iwth the Y-Wings 2-seater variant it seems more along those lines.
EU's placement of astro's is weird then... The Jedi Fighter's one is weird, and I think it was mostly a cop-out to have a dedicated astromech. Almost like they designed the fighter but later realized they didn't design it to support an astromech and Lucas wanted it to be able to... Simple answer then is to make it a dedicated on-board system with a dome... for no reason.
I'm pretty sure EU has Astro's popping up on ships in different places though, some toward the front, some to the back... I don't mind the placement really on the new Jedi Fighter... If it doesn't support a removable (full) droid then it's sort of a bummer. It leads me to believe Hasbro butchered the scale somewhat perhaps.
I don't mind the astromech being up front but I do think it bites if they don't make it so a full astromech fits in the socket. That implies an underscaled ship to me, which sucks.