I think the playoffs doesn't have much to do with the draft, except the champion drafting last. A 4th ranked finalist still picks before the 2nd seed for example who got eliminated in the quarterfinals. If someone doesn't want to get promoted and relegated, the safest way is to just make the playoffs. I've done it multiple times, and if I didn't want to go further I just set a weak lineup. But if someone decides to just have the PO game as a 50-0 WO, maybe the jersey sales could drop a little since the fans are dissapointed that their team didn't even show up to the game. Maybe a 30-40% decrease in jersey sales can be a penalty, it would effect in the next let's say 3-4 weeks. So it wouldn't be as strong as a boycott obviously, but it would lower the weekly income. But if there's a playoff walkover, I wouldn't mess with the draft. Especially if that team had a lineup for every regular season game, which actually affects the draft.
And I know we have that feature, but not everyone is a supporter