If, as you imply, you're already fit (you state your goal is to stay buff and strong, not get buff and strong), I don't think the reduced workout schedule foisted upon you by your job will cause you to backslide. If I understand your schedule, every two weeks you have two 2-day blocks off, and one 3-day block off. So even if you worked each bodypart only once per off-block, that would amount to working everything three times every fourteen days--an average of once every 4-5 days. This is frequent enough to where muscle loss will not occur (and gains are possible).
As for the split, you might consider the following:
--On the two 2-day breaks, work Upper Body one day, Lower the other. Focus on basic movements, and lift for strength/power.
--On the 3-day break, use a three-day split (maybe Push/Legs/Pull), and do BBing-style workouts--more sets, more reps, isolation movements, pump work, etc.
Finally, if you could sneak in some core and bodyweight work on your 'job' days, that might be productive as well. Best of luck.