The free attack sounds reasonable for single-attack classes like Rogue, but I don't think it'll hold up to the sniff test with multi-attack classes with the first option.
The second version is more reasonable but auto-advantage on any hit with the main hand is pretty unnecessary, IMO.
The part that makes DW balanced is the same thing that makes it less-optimal when compared to GWF, the opportunity cost of your bonus action to take another swing for the fences..
How would it not be up to snuff?
I disagree that it is balanced at all, hence the changes.
It's funny that you use the euphemism of "swinging for the fences" which is something you do with a two-handed baseball bat =). The feat cannot be balanced against the player it has to be balanced against other feats.