With this "sports director" thing, if results are poor, who gets sacked? The SD because of poor recruitment decisions and inadequate management of the manager and coaches? Or the manager, for failing to benefit from the SD's (presumed) wisdom and thereby failing to get good performances and results from players the SD strongly recommended? If it looks messy before it starts, it's likely to be messy when it actually does start.
If anything, rather than a sports director, I think an assistant manager is appropriate, with scouting and recruitment specified as part of his (or her) overall remit.