Pamela, I'm totally with you! There should be a networking table for people who just love Litmus LOL! Also, this will be my second year attending—it's so much fun!
My organization rents lists (and is even expanding the list rentals we have in place). I have tried to discourage it, but we have seen enough results that, for us, it actually does pay for itself. Because our inquiry gestation is so long (1-2 years), and our ROI for each individual conversion is so high (can't share an actual number, but it's a postgraduate education, so you can guess), if even one or two inquiries convert from a rented list, it's seen as being worth it. Also, for what it's worth, the list owner is a company that specializes in our industry, and they have great customer service for us and their recipients, so maybe they're an exception?
The list owner sends on our behalf, so the from name is us, but the unsubscribe language is theirs. As far as I know, we haven't shared any suppression lists with them.
Obviously, it's best to have as much of your text as live text as possible, but I think it's perfectly ok to use your branded fonts in your images when you do have words in your images. If Arial is not very similar to your branded font, you may want to test out how some other web-safe fonts look—here's a helpful website for web-safe font stacks with the best backups for mac and windows: http://www.cssfontstack.com/.
Additionally, depending on your customers, you may be able to deliver a branded experience to most of them using web-hosted fonts (self-hosting your font files, and calling them in your CSS). Litmus previews will help you see which devices they will work on, as well as preview backup fonts in the clients that don't support web fonts.
Of course, another option is to revisit your brand's fonts. There may be a web-safe font that is similar, or at least a google font that can be easily used across your website and email (again, where it's supported). This is usually not feasible for large organizations, but can be helpful for smaller organizations—or something to keep in mind if you ever find yourself in the process of refreshing the brand.
The prediction about context rang the most true for me. Additionally, I think emails will expire when they are no longer needed (think of a promotion that's ended or a flight that you've already taken), instead of the user having to delete them.