Not opposed actually, since it seems doubtful to me that officials can align the down markers and nose of the football to within one-half inch currently, but I expect there are some interesting difficulties to deal with.
For example, off the top of my head and probably obvious to everyone:
Seems like they'd want to keep something visual as an aimpoint for a player wanting to get out of bounds past the line to gain. That would need to be positioned accurately enough to minimize, um, disputes, so need some kind of communication or indicator from the automated system to indicate where to place the visual marker. How would one assure reliability in say, rain or heavy fog or snow?
How to ensure someone doesn't hack the comms or other parts of the system and fudge things a bit?
There must be other things that need to be taken into account.