I had this problem in a game I made a while back. This was my solution.
Player is standing on platform * Set platform jump strength to 100
Block opacity < 100 * Simulate Jump
* Wait 0.1 Seconds
*Set platform jump strength back to original
This meant he gave a little jump when the block vanished, but it worked pretty well. I'm just setting his jump strength to something low, making him jump, then setting the jump strength back.
Hope this is of some help