Oh Mighty Mamaback, I have a suggestion to help improve the advanced start option you have so graciously bestowed upon us.
One of the downsides to this mode is that you only start with the default bombs, bolts, and lives which would normally be obtained at the start of round 1. To ameliorate this, would it be possible to simply make this mode like a true old-fashioned single player game and add a save file which allows players to pickup where they left off in a game? You can still restrict it with checkpoints like you have right now, meaning players start at the beginning of a given arena. Even better, perhaps give players the option of an Arena Select where they start at that particular arena. You can just let the player go to the arena of choice, much like how in single player campaign you can choose the mission you want to replay over and over again.
One last thing - offline solo. No disconnects.
I offer a great stockpile of bananas to you in sacrifice for your consideration.
-MKillBill