50/50 can work but you need to be very clear with him about what that entails. Go through the matters below with him. (If he’s not willing to take time to do this, 50/50 will not work.)
Yoy need to clarify what the plan is- one week on, one week off? If not, what?
You both need to live close to the school and fairly close to each other. What’s the plan for this?
If he works full time, you need to know exactly how the kids will get to school & back in ‘his time’; & he needs to appreciate he will be responsible for this. What’s his plan? What’s his back up? You’re not going to be stepping in if eg he needs to work late one day.
You both need to accept that you need be able to communicate with each other regularly & in a constructive way- otherwise kids will be regularly exposed to unpleasantness.
Kids will need duplicate equipment and school uniforms at each house so they are not packing up each week. He needs to buy everything needed at his end. When will he do this? Does he know what to buy?
He needs to supervise homework during ‘his time’ & transport kids to weekly clubs & to visit friends & to dentist, doctor etc. If he’s not prepared to do this, kids will be at a HUGE disadvantage educationally & socially. This REALLY matters.
He needs to be prepared to build relationships with the school & be fully engaged with progress reports , conduct issues etc.
He needs to be on top of things like PE kit and school events that take place in ‘his time’. This means reading school newsletters & if applicable joining parents’ WhatsApp group.
He will need to do kids’ launtry ironing etc when with him, & deal with cooking for them & (if needed) packed lunches. They won’t just eat pizza.
The system set up needs to be consistent, reliable & diarised well in advance. He can’t chop & change his days/weeks - except in case of eg real medical emergency.
You need to know that he will be at home in ‘his time’, not abroad. He will lose the opportunity to make unscheduled work trips.
From what you have said it sounds unlikely that he will have the discipline to make it work. But it can.