You might try the AMEX platinum 2 for 1. Certainly the mileage accumulation and upgrade is legal. I think the trade one B in and buy two Y has serious tax concequences. The company writes off the B price, and you convert 1/2 to a non- employee. Does not sound good to me.

After that, they are going to start counting days of work and days of play and your business trips are not tax deductable. Last time I looked, over 1/2 of days away, including travel time, and weekends must be work days. Non-employees expenses must be pro-rated, and excluded.(even difference between a single room and a double room)

You do not want the IRS to look this, so find out how to stay very clean.