Switch Theme/Font via Keyboard Shortcut

Can you please add a customizable keyboard shortcut for quickly switching between (cycling through all available) themes and fonts?

As it is, I’m sticking with a single theme (Sci-Fi) and font (Consolas) all the time, although I’d like to be using other themes/fonts sometimes, for variety’s sake. But, it just takes too many button presses and taps currently to switch to a different theme/font.

(While we’re mentioning the topic: I’d also welcome a larger selection of fonts, particularly serif and monospace fonts, as I believe there’s only one of each available now. The ideal would be, naturally, the ability to use custom fonts of the user’s own preference, to be loaded into the app, as seen in some ebook-reader apps, for instance.)