The "home every night for dinner" thing is annoying but necessary for the way I play - if they were away for long periods of time they would miss too much of their family's lives. Most of my sims get a year old every two days - if a parent was only home at weekends they'd be away from their kids for 2.5 years!

As for the career progression, I imagine that they have different job titles depending on where the sim is going with that career. A sim who is heading for the top of the Science career for example would be a PhD student for the first few levels ("Field Researcher" is them doing all their experiments etc.) and "Science Teacher" is them teaching at a university either at the end of their PhD or as a post-doc, depending on how long they've taken to get promoted. Then all the titles from there are just creative ways to describe their work at a university or research institution of some kind. Whereas a sim who is only aiming to be a high-school Science Teacher is working as a Lab Assistant part time while studying for a Masters in school teaching and "Field Researcher" is a substitute science teacher who also works at a science museum/ outdoor activity place while trying to get a school job. Then a sim who just took the first job that came up to earn some money really is a Test Subject - and if they are competent and organised and the lab is seriously short of people they might get offered an actual role as a very junior lab assistant who does all the admin for the human test subjects and/or some data entry.

I have been considering this question myself as my sims are in the military (galactic fleet). Those in the galactic fleet work for a few months and then return home to the planets surface. I considered making “spaceship houses” in a vacation concrete based map where it is always night . They go in “vacation” when they are working on the ship with their crew. The problem becomes when I save my BV lot and they are still roaming around town as if they never left!! So what I have been doing is playing the full three day vacation in one sitting and return the crew home when the “vacation” (their month long work shift) is over

Interested to hear how others are doing workarounds for away work

You could temporarily give them Inge's prisoner token, so they don't show up on community lots while they're away.