In terms of security, choosing the oldest pool is a poor choice all of that was discussed thoroughly in this thread in which you participated. Do you support deprecating Sprout?
The turnstile is the most private way of moving out of sprout at the moment. Although, I remember that at some point it was discussed that it could be possible to issue the value stored in the sprout pool as a ZSA and let its owners redeem it by proving its ownership. That way you could zSprout in the orchard pool instead of turnstiling to sapling.
anyway, it’s unreasonable to support sprout in ledger, also the proving times of sprout make it unfeasible to be ran on embedded devices such as hardware wallets, so this discussion does not even classify as hypothetical.