The ideal format should be the same of Fifa Interactive World Cup (see here: ).
But just like other popular games that require skill and teamplay (CS:GO, LOL, DOTA 2, Rocket League) I think that matches should be played in PRO CLUB MODE with FULL MANUAL CONTROLS.
Furthemore, this is the smartest way to increase the popularity of the Pro Club mode and to encourage playing Full Manual.
Most important, game matches with these settings are way more exiting to watch bringing all the drama of the real football, unlike the usual 1vs1 kids playing with lame assisted controls (so boring!).