It's a good idea, but there's no need to make it too complicated in a football management game.
The player acquires a foreign language gradually based on the length of time spent in the foreign country. Although perhaps it could be easier for younger players.
Would there need to be language levels?
Such as level 1 (basic) acquired after say 1 season, level 2 (intermediate) acquired after 2 seasons and level 3 (fluent) after 4 seasons.