Promotions can have conditions. So you could create an upgrade promotion specific to a active plan. For example if it requires Plan A to be active then it would have no affect if user was upgrading from Plan B to Plan C for example. So you could for example create a promotion for each upgrade path (there's no limit on how many promotions you have). You can also set the promotions to be automatically applied and your users won't have to input anything; it'll simply auto deduct at invoice. However, this would be behaving basically the same as Prorating does (user gets their investment into Plan A transferred to Plan B ).

Do I just provide a 100% discount and then we manually monitor it to know if we need to issue a refund via Authorize.net? And if so, how do we match that up with CBSubs so if a client looks as past invoices they see they received a refund? Or can I enter a negative amount?

Hmm, CBSubs can't do refunds; you'd have to do them manually. I think in these cases you shouldn't bother with a refund if they downgrade to a less expensive plan, but simply give them that plan for free. It's typically not in a users best interest to be doing things like that, but be sure to inform them of the loss. At any rate if you'd still like to issue refunds you'd need to do so from Authorize.net directly.

One more question - I had a parent set up which charged the price, and then 3 children for the style selection. When testing this method (instead of all parents) I had unsubscribed to the parent but it left the child subscription there. Is there a setting that makes the child automatically unsubscribe if the parent is unsubscribed?

Child plans won't unsubscribe if a parent plan expires, but they'll wait for the parent plan to be renewed. In other words they'll be able to SEE their subscription, but it won't do anything until the parent is renewed. Child plans have to be unsubscribed manually just as the parent was. It does this because the parent could have a different duration then the children for example.

If the parent expired then expired the children automatically but the children still had a years worth of duration the user would be "short changed" and not get what they paid for. We've plans for future release to allow child to maintain same durations as parent and formulate a more "set in stone" relationship so something like unsubscribing parent could/would unsubscribe child. That's not available now however.

Is it possible to make a CB user field only required if someone has a subscription?

Absolutely, you can hide it entirely based off subscription using the CBSubs Fields Tabs Protection integration you can then edit your tabs or fields and select what plans the profile owner or profile viewer need to access the tab or field.