Select among the @BAKEs in a file?
This could be user-useful but would require an overhaul of the options.

Specify the shell environment somehow? -- NOT NEEDED
Could be nice, could be easy to implement with some different starter
command, such as @BAKE_ENV /bin/sh [command ...], but the power of
regular old /bin/sh alone should be enough for everything. Calling
a script is perfectly practical considering the rooting facilities.
Use Make or a script, this is nearing overkill.

Enviromental variables? -- WORKS, NO CHANGES NEEDED
No idea how the support is currently, should be fine. Anything more is
overkill, use Make if you need ?= and $(XXX).

Longer @EMBEDDED_BAKE handle? -- NOT NEEDED
Possibly a good idea for large binary files, but I would rather just
write the "Select among @BAKEs" feature than cheap out with an additional
handle. Besides, this is only useful for a gimick autonomous compile
feature. If I decided to write the @BAKE_ENV feature, I'd probably need
to also include a @EMBEDDED_BAKE_ENV which is a little ridiculous.
This will at best make me consider writing/using hashmaps, which would
be a techinical improvement, but definitely is overkill.

More Macros? -- NOT NEEDED
Luckily, with the rewrite to expand, this would be very easy to add.
But I don't know of any that wouldn't be overkill. If I ever think of
any that would be substantially useful, I might add them.

Kill globals. -- DONE
I'd need to first isolate them into bake_expand, which is a bit of a
pain but a thing I'll definitely do.