The big incentive for ditching games is to get better draft picks. In oour rotisserie leagues, we have eliminated/limited the incentive by doing the following: Teams which win money (i.e. top 5) draft in the last 5 places in the rookie draft. The rest of the teams are ranked in order of the standings for that draft (i.e. 6th place through 12th). The get the first seven picks in the rookie draft.

The bottom 8 records get into the rookie lottery for the first eight picks. The rest of the teams select in reverse order of record. Perhaps an idea might be to include all non-playoff teams in the lottery, with the bottom eight getting an extra "chance" in the lottery. It limits the effect of tanking games as much as possible.

I don't know if this provides food-for-thought, but I hope it does.