As I've said frequently on this matter, tying in the declaring of champions, relegation etc is NOT and never has been tied into the releasing of funds for league positions. Give the bottom 4 the minimum they would be guaranteed; for example give each of them the amount for finishing bottom. Give the top two the prize money equating to second place. Give Motherwell and Aberdeen the money appropriate for 4th place.
Get the vast, vast majority of the money out there to clubs now. You don't need to hold it back until positions are finalised. It can be fine-tuned at a later date.