Can you cast spells while under the effects of the Minimus Containment version of Binding? I assume RAI is no, but the Metamorphosis version is explicit that you can't, and Minimus Containment isn't. If the jar used for Minimus is left without a lid, could you get out?
My thought was to use Minimus Containment to protect my real body while I used Spirit Jars to keep myself in another body "permanently". I initially figured I could set "my soul returns" as the condition that ends the binding. But maybe I don't need a condition if I can cast spells, just say Minimus.
No... binding means you are out of action, sent to the showers, marking time in the penalty box. You can not do anything meaningful. and if the jar used for minimus is breached, it's the same as breaking a magic circle, the spell ends and you are wooshed back to your normal size.
All of these spells are PRISONS. Not means of making invulnerable redoubts from which to carry out actions.
Where does it say that breaking the jar returns you to your normal size?
I agree, the intent is that you imprison the subject. I'm just looking at the mechanics and thinking that isn't quite how they end up working out.
I do think you could probably use Minimus to keep your normal body from needing to eat or breathe and from aging. Since the target is a creature, might have some work arounds needed, like having contingent Magic Jar on yourself then casting the Binding. I think that would do it. And again, you can always set a condition on the Binding, like "my soul returns to my body" that will just end it if something ends up happening to your possessed body.
It's a really poorly worked-out spell, seemingly more meant for story-telling than actual use. Per the rules, you can cast spells and even live forever, inside or outside of your "prison".
But given how silly things would become, it's probably better for everyone if we just ignore this spell's existence.