I like the idea of amnestying 1 player for new owners, but agree with what someone said about the 50% buy-out in that the new owner would still be paying for the previous owners mistake by paying half the salary and not getting anything in return while someone else will probably grab that player as a free agent at or around the same price of the owner who had to drop him.
100% amnesty on one-contract would give the new owner a chance to get that player back, if they wanted too.
On the 2nd topic: I would define a "new owner" as one who took over a team before the new season begins.
I also loved the idea of a set time period to allow for extensions.