Can't take turns? Bye bye toy

I have 3 1/2 and 1 1/2 year old kids now. What we do:
1) I have a blocked off area where the big kid can keep toys that are too delicate/too small to be safe for the toddler or that are special and he doesn’t want to share with the toddler.

All other toys are out in the open and are for sharing. Whoever is playing with a toy first gets to finish their turn and the other sibling can have a turn once they put the toy down.

Whoever “ owns” the toy needs to keep it in their own space if they don’t want to share it.
If it is a jointly owned toy I would set a timer.

Set the timer for 10 minutes each

Easy. Take it away. No one plays if they can’t share/take turns.

Hi
Two sibling have one or two years age gap and they both fight over same toy.
How would you solve the issue.
One is 4 years old and one is two and half.