Really you should reword what you are asking for instead of asking to change the rules of undersized parties, you are better off saying:
"I want the option to enter a dungeon with fewer players but still have the same rules as a duty finder group."
So if you do enter with a level 60 they will get synced the same way they would in DF, you are then doing the exact same content as DF just with less people.

You can then change the name of undersized party rules to:
Rollfaceonkeyboardeasymode4.0archancemageoptimalrotation!