Would it technically and/or morally be better to use the ZODB instead? How much effort would the switch need (it'll be my first use of the ZODB) ?

You hit it on the head. The ethically proper, morally imperative, politically correct and spiritual fullfilling way to do this would be with the ZODB. Technically ... the answer is whatever works best for you. Personally I like the ZODB but a large part of that is that I'm learning Python through Zope and not the other way around. I'm far from being a Python Zen Master.