In Germany it's unreserved, you buy a ticket to that block and just go wherever you can. In Dortmund's stadium, for example, the lower part of their 'yallow wall' is an old fashioned terrace, it's only the back half that has railing in (which is what the FSF are proposing here).
Not really sure about your point to be honest. At most EFL clubs you can go and pay on the day so that's not an issue (the stadium still has a limited amount of tickets so people would have to buy early or risk the game selling out - like it is now). I don't really see how you can think it would throw us back to the 70's. CCTV is miles ahead of what it was, Britain has changed significantly in that time. If you went to Maine road you'll know that you couldn't compare the old Kippax to what would be unreserved standing at Eastlands? Considering you are allowed unreserved attendance at nearly every other event imaginable (including concerts and the magic weekend that have taken place at our stadium) I can't see it being a huge hurdle with police.