They'd make great emergency room surgeons. Glorified mechanics, not scared of blood or people freaking out, can evaluate/diagnose/resolve the issue while everyone else panics.
I'm sure there's a fun buzzword around all.. that.
ISTPs could also be strong as scientists. I would suggest that Ti-Se dominant function in type theory would suggest the most objective way of thinking. Se observes the natural world in its most realistic manner, and Ti makes logical sense out of it. That seems ideal for the scientific method. Although it is also ideal to have some INTPs and others on the team to be as daring in idea space as ISTPs can be in real space.
technical artist is a very good term. There is a beauty in what istps do that surpasses simple "mechanic". It appears to me as machinery in motion, with an eye for precision, detail and elegance, with meaning embedded in the final product, but an insistence on reality that allows for much more flexibility and adaptability in the final product than intps.
I always picture the ISTP as the lone silhouette walking away from the huge explosion, back turned... just kind of sauntering off knowing everything is fine now that they've attended to it and letting everyone deal with figuring out the rest...
My ISTP little brother is a scientist through and through. Has been ever since he was 3 and made observations of tadpoles in the muck.
I do like "realist". At least it's better than craftsman or mechanic