You should be fine. I've done it before. With the often unknown nature of business travel, I would think DL would recognize it as genuine travel and not an attempt to do something prohibited in DL's fare rules.
If anything, it
could be seen as:
Back-to-back ticketing—combining multiple overlapping round-trip tickets to circumvent Saturday or other overnight stay requirements.
http://www.delta.com/planning_reserv...jsp#prohibited