From what I've researched its a specific type of job in a lab not an intern or TA type of position.
You may be being overly literal.......
Literal? Only in that its an actual job that often requires training and certification but isn't alway a step on the path to becoming, for example, a microbiologist. Any more than being a nurse is a prerequisite for becoming a doctor.
Within the sciences, several different types of position might be termed "lab technician." In medicine, certified technicians are required, but in areas of biology not requiring patient treatment - such as DNA experiments with swiftly-reproducing animals (e.g. rats, fruit flies) - laboratory technicians are much less rigorously identified. A friend of mine actually became a biology lab technician for a professor at a world-class university during her first year of college, directly from high school with no training beyond AP Bio.
The problem with a blond lab technician other than Carol Marcus is that there is very little room for one in Kirk's history. Kirk was an ensign aboard the
Republic "some years" after Finney served as his instructor at the academy. He was a plebe in 2252, according to "Court Martial," so he entered the academy no earlier than 2251. Kirk was a lieutenant by 2255, according to "A Private Little War", so he must have reported Finney aboard the
Republic by then. He moved on to the
Farragut by late 2256 or early 2257, according to "Obsession." At some point in his lieutenancy, he became an instructor at the academy, met Gary Mitchell, and was steered toward a "little blond lab technician." He "nearly married" this technician.
If David Marcus was the same age as Merritt Butrick in TWOK, he would have been conceived in 2259. In view of the rest of Kirk's history, it doesn't seem likely that he would have nearly married two different women within the span of only two years (and conceived a child with one) - let alone nearly married two different blond scientists.
Even if David were slightly younger than he appears (at Butrick's age he would already be a 23-year-old PhD), there is little room for an additional relationship. Kirk and Areel Shaw parted ways by September 2262, harboring strong continuing feelings for each other (Shaw knew how long they'd been apart "four years, seven months, and an odd number of days" later). Their relationship certainly began before then; even if it was a short matter of days in length, the potential timeframe into which a second near-marriage relationship (aside from the then-non-Marcus lab technician) would fit is very limited.
(As it happens, if Carol Marcus was roughly BiBi Besch's age in TWOK, she would have been somewhere near 20 in 2259, a likely age for a PhD-bound biologist to have worked as a lab technician while pursuing her education.)