Kevin
This suggestion would take us back to the old "web only" game before August 2016. In that version of the game you had a slider to choose between 100% developing the car for the current season, 100% focusing development on next season or something in between.
Very few managers had a balanced design, they would have two teams in the league, one would be competitive this season, the other would be running around at the back storing up design for next season. Each season a manager would flip between his two teams to compete for the championship. As a result many leagues only had eight managers each with two teams.
Personally I wouldn't want to return to this strategy which is what would happen if this suggestion were to be introduced.
Yes, it would require some debate and trying to find a way to close of loopholes. Perhaps it could be a league option and the host could just kick out teams that they suspect are playing this trick