Unpopular opinion:
Inter, Juventus, and Lazio play once against each other in a round robin competition to determine who wins, with results from the regular season taken into account. Juventus start with 6 points, Lazio with 6, and Inter with 3 (seeing as they lost twice to us, and once to Lazio). No playoffs (we don't want to lose another final).
Game 1: Inter vs Lazio
Game 2: Juventus vs Lazio
Game 3: Juvenus vs Inter
Do the same for the teams from 4 to 8 to determine who will enter the CL.
Teams from 16 to 20 play against each other to determine who gets relegated.
9 to 15 can have a pleasant summer and prepare for next season.