So after hours of experimenting, me and Kryptek found a way to skip the Delivery Bag without the Tuner.
http://www.youtube.com/watch?v=D1I-7zTtnk8 My footage
http://www.youtube.com/watch?v=fzcxqKn7m9I Kryptek's footage
Now there's a couple of things that might make this less useful, but I believe in time it could be perfected to save time. First, using the chest we normally use to climb to Medli after Earth God's Lyric requires us to get another chest, I figured this workaround:
Crescent Moon Island Chest Storage. The best thing would be if we could climb to Medli without Chest Storage, but seems like it's impossible with current strats. I hit the fish on that but he can probably be avoided (-30s). Also this was not done in perfect conditions so further research is required.
Second, to get the chest down in the first place you need a Hyoi Pear. So 20+10 extra rupees and a trip to Beedle. But in my opinion this isn't such a huge time loss that we shouldn't attempt to utilize the skip.
What I figured so far:
The Road to Rito
-no rock jump
-no Quill cutscene
-Delivery Bag Cutscene
+Drop the chest, storage, go around the island and hit the loading zone
+ 30 Rupees + Bait Bag + Hyoi Pear
+ Extra Chest Storage from nearby island (SS to Crescent)(?)
So, it's not definite if it's worth going for this. The timings still need to be tested further.