The most we should hope for would be a "loan market" with open bidding similar to the transfer market, but the player would return after a specified number of days (30 minimum, 100 maximum?) and the minimum bid would be set as something like this number of days x 100 G (3,000 - 10,000 G) for all players. At least it would be no easier to cheat than with the regular transfer market, and it would provide not only a new source of income, but a way to pick up high-potential players relatively cheaply, if only for a little while.