That post was getting lonely! I never did get any further; I switched to Xfce instead of Gnome. An XfceDelayedAutostart.sh script is working simply, as hoped.
One suggestion: what happens if you move everything off the desktop? Does Gnome start any faster?
One solution for what you want to do would be to write a shell script to do it, run from the autostart feature. The most common way for shell scripts to participate in the desktop GUI is with zenity but the little-known yad is a lot easier to use and more powerful.
If the encrypted drive is external it might be possible to automate everything -- so when it is plugged in you are prompted to authenticate and, when that is successful, qBittorrent is started.