I give one hell of a lot for all that you mentioned.
If Riley is fired before the end of the season (Say early November), it's no different for him and his wife than if he were fired at the end of the year. We aren't going to a bowl game he could coach in and he will still be paid something like $2.5 million till 2021.
His assistants aren't dummies. They know a change is going to be made and none of them will be fired till after the season no matter if Riley is fired early or not.
The players aren't dummies. They know a change is going to be made. To me, it sure doesn't look like Riley does any in game coaching anyway. So, his absence shouldn't be horribly missed in the last few games. Other than that, all other position coaches and coordinators will remain the same.
So, I fail to see how firing Riley before the season or after the season has any negative affects on the already established situation.
Now, to your point, I've fired quite a few people. It always should be done with the utmost respect and dignity for everyone involved.....but, that doesn't mean it's not going to happen.