No 1 - You dont make special teams unless you take the snap are a punter or take field goals.Special teams is made up of other squad players -running backs wide recievers etc.There is no punt returner as a position only!!
No 2 - San fran have 2 deff rb's ahead of hayne.A third if fit and now one they drafted.You usually dont draft a guy in the 4th round without plans to be in the squad.
No 3 - At best if Hayne was to make it lets say as 3rd or 4th choice. There would be 100's of guys capable of beeing a teams 3rd or 4th choice. The lower down the ranks you get the higher the amount of guys in that class. Now if you where the coach would you chose Hayne, a guy with plenty of money who can go back home and earn 1.2 million a year or some guy thats come from poverty where 600k would change his life completely. And if cut him he has a high chance of going to a min wage job.
We are talking two guys who are the same level. Unless the coach believes Hayne is good enough to be a star i think it would be selfish on both Hayne and the coach to chose Hayne TBH.
Think of it like a job. Unless of course the whole thing is just a media stunt