The probabilities should be based on your record over a couple of years (so, a team that won 50 games one year and 10 the next would have the same odds as a team that won 30 in both seasons). That way good teams that have their best player injured could be separated from those that are truly bad, and teams that want to tank would have to do so for a longer period of time, making it much more of a financial risk.
There's always the risk of teams doing hat the sixers re doing and being consistently bad for few years, but after a year of tanking without even getting a chance at a good pick, fans would be less forgiving.