Note that you're probably on your own for support, if you stray off the beaten path. If you buy a Chrysler car, and substitute a Ford engine and GM transmission, your Chrysler dealer won't have the tools/parts/knowledge to support your setup.
Disabling ffmpeg means you'll lose audio/video abilities on PM. I don't know how it'll interact with everything else, but the source code does include an option to disable ffmpeg. You'd have to insert the following line into your mozconfig.
ac_add_options --disable-ffmpeg
I prefer other ways of reducing the size of the final program.
1) Do you really need devtools? If not, insert
ac_add_options --disable-devtools into mozconfig.
2) There's a tweak in GCC to minimize the binary size. No, I'm not talking "-Os" which slows down execution. There's a short discussion on the busybox mailing list...
...about how to minimize binary size. busybox is meant to operate in memory-constrained environments. The busybox devs are pros, and wouldn't do risky stuff. I add the following line to my mozconfig
ac_add_options --enable-optimize="-O2 -msse2 -mfpmath=sse -fomit-frame-pointer -pipe -fno-unwind-tables -fno-asynchronous-unwind-tables"
BTW, at home I run Gentoo linux, where everything except a few proprietary binary blobs (Flash plugin, Nvidia video drivers, etc) is built from source. I've been running with "-fno-unwind-tables -fno-asynchronous-unwind-tables" for over 5 years. If this was going to cause problems, I think I would've "found out the hard way" by now.
