B is possible for my job, I started job doing something similar, worked part time (20 hours/week) for benefits, then worked PRN for the other 20 hours, or choose how many I work by what I sign up to work
But I work a normal 40 hour/week now but work 4-10 hour days so I have Friday-Sunday off every week.
I'm no where near FI, but I plan on going the B route when I'm about 5-8 years out from RE. Except instead of less hours/week, I'm thinking I'll just work 1 month less per year and increase it until I'm at a 12 month vacation then it's RE. But doing a variation of this or B, you end up working a bit more, notice the extra year in the A vs B.