Add a Heist Take counter ticking up just like GTA V (The Online portion doesn't have the ticking, it's instantaneous I think) whenever you secure bags or grab Loose Cash.

https://youtu.be/uiBBx24eiOw?si=lNpRQkTWHTzLPmpJ&t=124 (2:04) check the bottom right corner.

Another example: https://youtu.be/lOArUsjH5DQ?si=994-N7bMKzFn68sn&t=237 (3:57)

Mio, a developer on PD3, told me that payouts are based on Heist Completion so it might be difficult to implement?