IMO, creating a log entry for each purchase defeats the purpose of establishing the $2,500 per day limit in order to avoid maintaining the MIL. You might also be hard-pressed to obtain this info since it is not required, especially if the purchaser knows this.
If you are looking to strengthen what you have described in your post, you might add to your procedure to OFAC screen the payee along with the purchaser.
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I've just writed a wrong.