alfio, i agree with you on allowing only one bet. though sometimes only a win or a draw isn't enough. on high risk games you want both. you can very easily solve this by providing double-chance odds; 1X, 2X or 12.
1X= a draw or home win
2X= a draw or away win
12= home or away win
those odds are probably available on the site you get them from. they are also usually about twice as low than a single outcome bet. check it out.