flashize-env depends on flashize-ext, so issue #1 fully applies.
also, if you sidestep the unzip issue, toybox cpio adds problems of its own.
for flashize-env to support toybox, it looks like one of these options is needed:
dumb-down flashize-ext (including its interface) to always extract the complete zip to ram (awful),
or completely reimplement flashize-env and make the update script be a shar (self-extracting shell archive) that is compatible with toybox limited environment:
the script can either carry a zip, tar or cpio file if toybox zip/tar/cpio support works well enough,
or directly carry a naked busybox binary, "install" it:
and make busybox the "complete" flashize-env environment,
or make flashize-ext depend on depend on this "micro" environment, and have the full flashize-env run on top of flashize-ext as a fourth layer (not a third layer as it is now).
flashize-env depends on flashize-ext, so issue #1 fully applies.
also, if you sidestep the unzip issue, toybox cpio adds problems of its own.
for flashize-env to support toybox, it looks like one of these options is needed: