- "Will be abused by mappers and prob result in an underground beatmap sharing network. That's kinda already the case with unsubmitted maps, but I am not a fan of pros keeping maps to themselves and this will encourage that so much more."
You think they will go through the trouble of playing offline for those maps? If yes then what's the difference to unsubmitted maps? Someone could make a nice map and keep it to themselves because they don't want to share it, like people craft practice/ warmup maps very often and they don't get shared. I don't see a problem with that
For me, I have often encountered problems on my WIP maps that need to be resolved before I go on, since I would risk repeating the mistake and then having to redo the whole map. Since I am against uploading unfinished maps I like this request. It would allow me to show my maps to someone else and consult them without uploading my unfinished work publicly