This sounds like a pretty good idea. I think it may be problematic that your node holds so many pieces, it likely will not take too long until the first piece for which your node is the longest one offline would need repair. But I would say it’s worth looking into.
You could also choose to repair data using funds from escrow from the offline node. That way you don’t have to DQ a node right away, but only after a significant chunk of escrow is consumed for repairs. Once the node is back online you could drop it back to a previous escrow level based on how much money is used for repairs in the mean time. So if you’re in the 100% payout 0% escrow period, you drop back to 75% payout 25% escrow, to recover the now used escrow amount.
Both option require quite a bit of engineering to make it happen, but I think it’s doable. The question is, is it worth putting the effort into? That engineering time could be spent elsewhere.
You get back all the money in escrow. This can be a significant amount. So it’s definitely worth going with graceful exit over just leaving.
For Storj, there is almost no cost for a graceful exit as your node would transfer data directly to other nodes and no repair is needed. Since that egress traffic isn’t paid, the only cost Storj would have is the traffic with the satellite to coordinate these transfers. But that is probably negligible.