Great idea; it would also help if we could choose their settings (more defend/attack, long shots, run with ball, & on penalty area) as well, since subbed in players seem to have all these settings set to default, which may not be the best choices.
Also, it can be annoying if you sub out a player you've set for free kicks, corners, target man, etc. because once they've been subbed out, this setting turns to default, which seems to randomly allocate the duty among the players on the field, rather than have the best-suited player perform them. While it would be nice if the game engine automatically selected the best player for the task at hand, it would also help if these settings can be altered for substitutions. Even a 2nd choice option for each of these settings should achieve this.