So what combination you thinking for next year?
Depends on the availability and development of players.
I think Madden and Doueihi is probably the best option currently but I believe there is more to it than that.
Firstly, who is the 13? I believe the style of player you have at 13 determines what style you want from your 7. If Twal plays the bulk of the minutes there, I think that locks Madden into the 7. If someone like Mann and/or Brailey gets big minutes through the middle I think Fainu/Doueihi is probably the better halves option, assuming Fainu proves he is up to it on the training field.
Madden you know what you will get, which admittedly isn't great but he will provide direction.
I hope Fainu makes an irrefutable case for a starting jersey over the preseason. I think he is our future halfback and would not be upset to see him start there (or 6). So long as he is starting in the halves in either grade I won't be upset, not used as a lock off the bench.
Doueihi is undoubtedly in our best 13 but firstly has he earnt the trust of his teammates to be selected? I'd be tempted to give him reps at both centre and backrow (as well as obviously 6) over the preseason to teach him some humility and ensure he doesn't feel entitled to a starting spot. Just keep him well away from the 7 role.
Next is there a centre or winger out injured, as I think centre is his best spot. I'd happily start him there if any of the outside backs were missing long term (just not chopping and changing between centre and 6, must be long term injury cover) and fit the 3 of them in.
Plenty of options but sadly no-one demanding selection currently.