I thought I had bookmarked something that did what you're looking for, but no such luck, although it sounds familiar.

Searching MacUpdate turned up MountWatcher ($18) which may be useful if I'm understanding it.

It seems to allow you to set a separate user name and password for each volume, so (presumably) dismissing the p/w pane with no entry would prevent your drive from mounting.

Ah ha! Found it... Prevent a volume from mounting at boot, but I don't know if it affects an option-boot. (Also, it's from 2012.)

Hope this helps.

The new Great Equalizer is the SEND button.

In Memory of Harv: Those who can make you believe absurdities can make you commit atrocities. ~Voltaire