Short answer: no the airlines don't give a
at which 'airfield' you have trained at. How much scheduled airline traffic do you think Oxford Kiddlington gets? Doesn't seem to have too serious an impact on the well being of a little flight school there though.
The best thing that you can do for your CV is to find a school where you feel comfortable and work your socks off during your training.
Exeter has an ATZ and is situated directly beneath an airway. The fact that it does not have a slab of Class D around it like Bristol etc is really no bad thing when you are training, believe me. During my IR I used Bristol, Cardiff, Bournemouth and the Channel Islands for away approaches, so fear not- you will get plenty of exposure to controlled airspace. Exeter also has a full range of Nav Aids and provides a full radar service so officialdom is very much there if you desire it, just without the restrictions that go with a zone.
If you go and look around these places, ask them these sorts of questions. At Flightpass see if you can speak to Jerry, he is a real mine of information.
It certainly did not affect my employment prospects and think you will find many others who trained at Exeter who will testify to its merits as a training airfield.
All the best,
NF