The only twist I can see possibly happening is the father had a hidden clause. That if MC stays with Monica and family there is another pot of money that is higher, and he proves that he wasn't money grubbing like his father. But that seems farfetched.
Though you do have a good option there. i see a couple more that would be fun and others that could be a nightmare.
The non disclosed task you mention in the will for MC is most likely. though not sure your task listed is the right one but I yet to decide on the direction,
but it may be linked to whom you ask to marry.
1 hidden task "get Elaine pregnant" Elaine lied to Donald and can get pregnant, but he knew and if Mc proves this ....
2 hidden task "fuck them all" that way you need to have sex with everyone at least once in the game. (dark side of this)... The will reading discloses all his escapades to all present and he looses all the girls over this.
3 Monica still has a secret to tell
4 this was all a farce by Donald because he knew Bella's plan and wanted to watch her go about her deceit then give it all to MC to do as he see's fit
it all true but his marriage and Child change it all.
5. there is a secret to be discovered in Debbie's home life. that has implications on MC's life
6. the one that is not these.