Okay, this answersr my question as to why coins and cred blow up if the connection to Rock Central is severed. Interesting approach to handle all of that on their side, and we've already seen how it allows them to adjust various things without requiring a patch.
Also like that a "full" loadout costs 50 coins more than a 5-star performance. It's possible to 5-star many songs with the right combo of two power-ups, so if you go full bear on a song you take a SLIGHT ding on your coin count if you don't Gold Star it.
And it makes "grinding" less of a chore, as you can play a song once for at LEAST 4 stars without any powers and get enough coins in return to be able to start testing different loadouts and going for 5 (or Gold). And I like that, as typically my first run through a song turns into me flailing around for powerups as I get to know the various note sections and which parts I should try to focus on during the song.