My idea is this:
The beginning of the season (say within the first few days) indicates the club is a team goal this season.
Objectives can not be modified during the course of the season.
If you are lucky to meet the objectives, sponsors shall pay the higher amount.
Additionally, the publication of the objectives of the club, if not yet signed agreements with donors, they may slightly affect the amounts.
(say club which aims to fill 3 positions will šiektiek more than that, which aims to fill 5 positions)
However, if the contracts signed with donors, and raise the goal is not met, the image of the club is reduced dramatically and the future goals of the sponsors see netaip well.