There are a couple of options. The first, which you mentioned, is using BBCode, of which, honestly, I’m a big fan.
The other option is to move your format-heavy stuff to your troop forum here on Discourse (which does what you’re looking for), and just use the Scoutbook messaging to send links to the forum thread on Discourse.
The second option also lets you see how many times your thread has been viewed, which you wouldn’t get from an email blast. I don’t know if that’s important or not to you.
