I’ve opened mine at least a dozen times (and mostly from the top) with no damages so far. But I see that in general opening the case puts rather high strain on the material.
What do you think: might the two-part case developed by @dvl be an alternative or a good basis for a new FP2 standard case (maybe enhanced by a kind of snapping mechanism to avoid that the two parts slide apart when you pull it out of a trousers pocket)?
Then we could add it to the FP2/3 wishlist started by @paulakreuzer.