[W]hen you are dealing with lots of different systems,
and especially
 those with limited CPU/memory/storage, compiling everything from
 scratch (as with Gentoo) just isn't a viable solution. 
I don't see why not; it's how I set up my own machines.
...well, I don't know how limited your "limited" is.  I have a few
machines too small to self-host; those, I simply don't run a
full-fledged OS on.  Perhaps this stance simply reflects a gap in my
computer collection, the sort of thing for which 256K or 512K of RAM is
a reasonable memory load - I don't really have anything between the
really tiny machines with the likes of 256 bytes of RAM and 8K of flash
and full-blown machines with 16 or 32 megs of RAM and at least a few
gigs of disk.
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