Military personnel would obviously be the one big exception. It always has been. Military absentee ballots generally work well (except they failed big time in 2000).
“People often take work assignments away from home for months at a time” — the keyword there is HOME. People have a home. If you change domiciles, it isn’t that hard to go re-register to vote, get your sample ballot by mail, and go to your polling place. It doesn’t matter one bit how often you work in an office or work from home.
Elderly shut-ins can be visited by mobile vote registrars for registration purposes or to collect a ballot. Or they can use the limited traditional and legitimate UNCOMMON absentee ballot. I used absentee ballots in probably 50% of the elections I voted in over a three decade span because of extensive business travel.
The most mobile people are the homeless. Frankly, without a HOME, you shouldn’t be allowed to vote.
I did not pass any judgement of whether any of my ideas are actually doable. Some probably are, some not. But if we don’t put a strong stake in the ground, we’ll never get anywhere. It’s an old negotiating tactic to put in items that you know will be rejected by the other party and then you can wail and moan about giving them up.