"Other than potential discrimination in operation for the timing of deposits, does anyone see a problem funding before year end and immediately converting to Roth?" I can't get to the Roth conversion, because the deposit scheme you propose fails miserably, IMHO. Plan has an allocation method. Contributions must be allocated according to that method. Making a contribution just for the owner on January 1m whether or not he converts to Roth, just isn't acceptable.
As the AFLAC commercial guy says when asked if the duck kicking the golf ball into the hole is legal, "That's a big fat NOOO."
Others may, of course, disagree.