This is magnified even more if you make it best 10 or 12. Everyone will have Walsh, Oliver, Gawn, Grundy, Miller etc. and the scores will be too similiar to even bother.
At least best 18 would force more varied strategies, but you would have to have unlimited (or a lot of) trades to re-balance going into round 1.
A DGR scenario would again see the better SC players gravitating to very similiar set-ups. If you didn't maximise the DGR potential, history (in other fantasy sports) says you will struggle.
I think unlimited trades to reset is the best of a poor field of options. If Walsh, Oliver and Miller have all scored 150, does everyone grab them or do you leave them out with a bye pending? The lack of knowledge re rookie selections for the 10 teams that don't play Opening round, will cause a lot of people to drop off if they cannot reset their teams significantly.
As you say, I think it is highly unlikely they exclude OR entirely. It makes the usual planning and tinkering a bit different because we can't work around the normal best 30 parameters.