With the current selection of Magazines I think there is a 1% chance that Futanari will be coming from any of those (I am being generous when I say that, it's pretty much 0% in my honest opinion)
If FAKKU starts getting some Circles that produce Futa to agree to release there Doujins on FAKKU that would be the quickest way to get some Futa.
Normally I would say go to the
Offical Book Sugestion Thread to request that a specific book be licenesed, however if you haven't already purchased a book on FAKKU I do not believe you can post in that thread.
I would say send a personal message to Jacob and just state that you are mostly looking for Futa, and maybe include some of the circles, artist, and books you would particularly want.
Also to my knowledge there is one other place to get leagal Futa Doujins
On 2-D Market, that links to their Futa page, there are only 5 Doujin for sale but they also do the whole legal sales thing. I am sure that you since you subscribe here you would rather get it all here, I just wanted to point out another legal place to get some Futa, also those Doujins are very cheap, the most expensive one is a 3 part omnibus for 3.99€.
Hope this helps a tiny bit.