No need for all this at all
Firstly, let's not try to eliminate TOO many of the "human errors" in football. Chanting "The referee's a wanker" is part of the game as much as anything (In fact, it's probably the only chant that EVERYONE knows the words to, and can join in).
Leave offsides, handballs, fists to the fizzog and the like to the human component, and post-match review. Let's restrict the tech component to "Did the ball cross the line Y/N".
Then, let's not dump a load of cash into systems that rely on tracking chips and the like. All that's needed is a quick-playback video system, which can be used by the 4th official to speedily review any situation between the sticks. In cases of any doubt, play can continue until the ball next goes out of play, giving #4 a chance to tell the on-pitch ref if a goal was scored.
Hawkeye is fine for tennis and cricket, where the position of the ball is put in doubt on a very frequent basis, and constant vid-checks would be a real drag in proceedings. In football, the goal-line is crossed much more rarely, the ball most often finds the back of the net thus not necessitating a sophisticated system. Also, the ability to show the crowd visual replay of the ball crossing the line to confirm their suspicions (Whether on big screens in a prem/cup stadium at the time of play, or highlights on the League Show a few hours after the event) will always be more accepted than a graphical representation of the ball crossing a graphical representation of the goal line.
The expense of any system used can be limited by only having it used in the top league of each nation, play-offs, QF and up in national cup competitions, and all the way through international tournaments. That should still leave plenty to discuss in the pub about how Accy Stanley didn't get promoted because the ref didn't see the ball cross the line in the game against Wycombe 3 months ago which would have seen them scrape into the last playoff spot, etc.
Oh wow, this post is far too serious. Um, Playmobil recon or it didn't happen, Bulgarian Airbags for everyone! and such.