Personally I think it's a great idea to have a LFR at 60/70/80/85 because
1) Bring back the content that we had good memories with
2) it will give the chance for people that haven't experience a certain exspanion or raid at the right level
3) could bump up the subs for blizz = more money
4)no need for vanilla, tbc servers only etc
.One problem that might occur, is gathering 25 people so maybe introduce 10 people.
.loot system could work still like it does in mop.
.for the rewards once you complete a LFR, you could get gold, special tranmogs bits or pieces of gear to help you increase your chances of loot, also give JP to obtain tbc,wotlk,cata vendor items.
Like to know people opinion