I wonder how large the SD card is? I once transferred the articles from August 2008 Wikipedia archive (HTTP format) onto a 16GB SD card using SquashFS; the actual filesystem image was about 12GB. You could access it with a normal web browser, but of course none of the special pages (e.g. search) were functional. I had to optimize the mksquashfs tool to allow it to handle that many files without running out of memory; support for insanely large compressed filesystems wasn't among the developers' priorities at the time.
Luckily I had over 200GB of free space at the time, as the format of the official archives precluded extraction of individual files on demand. Once I got it into SquashFS form, however, updates were trivially accomplished via FUSE-based union overlays.