I noticed the added and modified leagues/cups just use the ABBA penalty system if a match is undecided. In reality that has been abandoned a few years ago. Also it skips extra time, which is not correct. On top of that I believe the away goal rules have been abandoned last season, for the play-offs as well.
It should be Extra time + regular penalties. Except the Johan Cruijff schaal of course, which goes straight to regular penalties.
Also may I suggest adding all the amateur teams that are attached to a professional team to the "Not allowed to promote" list in the Tweede Divisie? Such as Ajax Amateurs and SC Feyenoord. So if they do suddenly end up in the Tweede Divisie, that is as far as they can go because it is the highest amateur tier.