However, this is my constructive negative feedback - I don't think it will work because of this one piece here:
Pause if you know you'll have less money this week, deposit a bulk amount if you'll have more, even let friends and family deposit.
I tried doing this in a rather "manual" fashion by setting up a recurring monthly deposit into ISAs. The reality is - the freedom to turn it off is a huge anti-pattern to saving money. You need to make it very difficult to have the user turn off their dripfeed. Perhaps they have to make a call, or maybe they get penalized? Either way - I see this as your most important "anti-feature".
I would also question the commercial model of this - you're going to take a cut as well as GoCardless. It'll be interesting to see if people are willing to pay for that. However, what would be interesting (potentially) is to have a model (similar to financing) where the actual item is purchased through your platform. This will get complicated, but maybe there is a way to undercut the traditional micro-financing models that exist today?