One big drawback:
On * you get lounge access with * Gold which is given at the second level of participating programs that have 3 elite levels (i.e. AC Élite, UA PremEx, etc.). Similarly, OW gives lounge access for OW Sapphire (for AA Plat, BA Silver, etc.).
However SkyTeam only gives its elites lounge access with F and J (which they would have anyway!), limiting Y access to Elite Plus, for which you need DL Platinum.
(However guaranteed reservations alliance-wide is a step ahead of both OW and *).