Thanks to those who posted about the Russified firmware.
I probably should have thought twice, having the 350-which-has-no-SD-slot-for-recovery, but I was recklessly bold and it worked well enough for me. I love being able to change the default font whilst letting EPUBs keep their embedded fonts (if they have any), the screenshot feature, and the customisable button functions. After experimenting with a lot of serif fonts, I've settled currently on Droid Serif, though I think I'll switch between Georgia and Fontin occasionally.
1st: Droid Serif