There is a lens adapter being made that allows for drop-in filters on Sony A7 cameras. If I put a Nikon 14-24 on there, I could use filters without having to carry a huge and clunky front filter kit. The weight saving of the entire camera would come down by a large margin. Very tempting to look into for my long-distance landscape photo hikes. Now to just get over the poor battery life and poor controls of the A7 cameras... 
http://dc.watch.impress.co.jp/docs/news/20160204_742226.html?ref=prss
http://dc.watch.impress.co.jp/docs/news/20160204_742226.html?ref=prss