we have spent well over 50% of our time out of the uk in a number of different places. if you are a teacher and are wanting to work in sce schools, you need to be an sce teacher. you can't apply for this job for specific schools. so you are ok if you're in the uk, but not o'seas. lots of wives are teachers because they met their husbands when they were sce teachers living in the mess (officers mess).
nurses - again, ok in the uk, but not o'seas.
honestly? you do whatever you can find, wherever you find yourself. and less than two years later, you fetch up in a new place and start again. 
that is, if you can find someone to hire you because they know you're leaving again, and if you have jumped through whatever hoops are in force about employing foreign workers.
i'm a bit confused though - surely you are not planning on retraining? i mean, most of these 'career' things you're looking at a lengthy period of retraining... or at least a pgce for a year?
the thing about studying as a trailing spouse, is (again) that you move. i've been trying to finish my masters for some years. 
interesting that someone mentioned the ta. i'm not army (dh is), but spent some time in the military, and joined the reserves some time after i left. whilst we were in the uk it was easily the most lucrative employment (particularly as with my skill set i picked up 6 month mobilisations which came with paid childcare) but you do run the risk of them being to drier, sandier climes rather than the nearest military facility to your quarter.
on our patch currently, about 10% of the wives work (in low paid unskilled jobs. i am one of them. my hard-earned first counts for diddly squat
). we have unemployed (and unemployable) teachers (lots), nurses (lots), physiotherapists, lawyers, civil servants (lots), ex-mil officers (lots), and a russian princess.
oh, and a podium dancer. mostly, as an entity, here, we breed and lunch. (i use the 'we' loosely - have completed my childbirthing duties and as a worker, am unable to 'lunch'). i have seen this replicated in every o'seas posting...
there are of course those who are far less mobile and manage to engineer multiple uk postings around commutable distance - or who are established enough in their career to facilitate career breaks around postings etc. we haven't been in the uk that much, so i have to say out of the hundreds of army (officers) wives i've met, i can't think of a single one that has enjoyed a 'career' in the civilian sense. 
please find something! anything! (and then tell us me what it is!)
anything freelance internet based, anything very very very mobile and not dependent on local employers.
i know i sound like a cynical jaded old hag -
but this is a very real issue. i just haven't found the answer yet. certainly not for o'seas postings anyway. and i've been looking for some time. 