diff --git a/Cargo.toml b/Cargo.toml
index 78c001274..d2c941182 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -14,118 +14,14 @@ autotests = false
 [features]
 default = [ "feat_common_core" ]
 ## OS feature shortcodes
-macos = [ "feat_os_unix" ]
+macos = [ "feat_os_macos" ]
 unix = [ "feat_os_unix" ]
 windows = [ "feat_os_windows" ]
 ## project-specific feature shortcodes
 nightly = []
 test_unimplemented = []
 ## feature sets
-# "feat_os_unix" == set of utilities which can be built/run on modern/usual *nix platforms
-feat_os_unix = [
-  "feat_common",
-  "feat_os_unix_musl",
-  "feat_os_unix_utmpx_required",
-  #
-  "stdbuf",
-]
-# "feat_os_unix_fuchsia" == set of utilities which can be built/run on the "Fuschia" OS (refs: <https://fuchsia.dev>; <https://en.wikipedia.org/wiki/Google_Fuchsia>)
-feat_os_unix_fuchsia = [
-  "feat_common_core",
-  #
-  "chgrp",
-  "chmod",
-  "chown",
-  "du",
-  "groups",
-  "hostid",
-  "install",
-  "logname",
-  "mkfifo",
-  "mknod",
-  "nice",
-  "pathchk",
-  "stdbuf",
-  "tty",
-  "uname",
-  "unlink",
-]
-# "feat_os_unix_gnueabihf" == set of utilities which can be built/run on the "arm-unknown-linux-gnueabihf" target (ARMv6 Linux [hardfloat])
-feat_os_unix_gnueabihf = [
-  "feat_common",
-  "feat_os_unix_musl",
-  "feat_os_unix_utmpx_required",
-]
-# "feat_os_unix_musl" == set of utilities which can be built/run on targets binding to the "musl" library (ref: <https://musl.libc.org/about.html>)
-feat_os_unix_musl = [
-  "feat_common",
-  #
-  "chgrp",
-  "chmod",
-  "chown",
-  "chroot",
-  "du",
-  "groups",
-  "hostid",
-  "id",
-  "install",
-  "kill",
-  "logname",
-  "mkfifo",
-  "mknod",
-  "nice",
-  "numfmt",
-  "nohup",
-  "pathchk",
-  "stat",
-  "timeout",
-  "touch",
-  "tty",
-  "uname",
-  "unlink",
-]
-# "feat_os_unix_redox" == set of utilities which can be built/run on "Redox OS" (refs: <https://www.redox-os.org>; <https://en.wikipedia.org/wiki/Redox_(operating_system)>)
-feat_os_unix_redox = [
-  "feat_common_core",
-  #
-  "uname",
-  "chmod",
-  "install",
-]
-# "feat_os_unix_utmpx_required" == set of utilites requiring utmp/utmpx support
-# * ref: <https://wiki.musl-libc.org/faq.html#Q:-Why-is-the-utmp/wtmp-functionality-only-implemented-as-stubs?>
-feat_os_unix_utmpx_required = [
-  "pinky",
-  "uptime",
-  "users",
-  "who",
-]
-# "feat_os_windows" == set of utilities which can be built/run on modern/usual windows platforms
-feat_os_windows = [
-  "feat_common", ## == "feat_os_windows_legacy" + "hostname"
-  ]
-# "feat_os_windows_legacy" == slightly restricted set of utilities which can be built/run on early windows platforms (eg, "WinXP")
-feat_os_windows_legacy = [
-  "feat_common_core",
-  #
-  "arch",
-  "nproc",
-  "sync",
-  "touch",
-  "whoami",
-  ]
-## (common/core) feature sets
-# "feat_common" == expanded set of utilities which can be built/run on the usual rust "tier 1" target platforms (ref: <https://forge.rust-lang.org/release/platform-support.html>)
-feat_common = [
-  "feat_common_core",
-  #
-  "arch",
-  "hostname",
-  "nproc",
-  "sync",
-  "touch",
-  "whoami",
-]
+## (common/core and Tier1) feature sets
 # "feat_common_core" == baseline core set of utilities which can be built/run on most targets
 feat_common_core = [
   "base32",
@@ -189,6 +85,130 @@ feat_common_core = [
   "wc",
   "yes",
 ]
+# "feat_Tier1" == expanded set of utilities which can be built/run on the usual rust "Tier 1" target platforms (ref: <https://forge.rust-lang.org/release/platform-support.html>)
+feat_Tier1 = [
+  "feat_common_core",
+  #
+  "arch",
+  "hostname",
+  "nproc",
+  "sync",
+  "touch",
+  "whoami",
+]
+## (primary platforms) feature sets
+# "feat_os_macos" == set of utilities which can be built/run on the MacOS platform
+feat_os_macos = [
+  "feat_os_unix", ## == a modern/usual *nix platform
+]
+# "feat_os_unix" == set of utilities which can be built/run on modern/usual *nix platforms
+feat_os_unix = [
+  "feat_Tier1",
+  #
+  "feat_require_crate_cpp",
+  "feat_require_unix",
+  "feat_require_unix_utmpx",
+]
+# "feat_os_windows" == set of utilities which can be built/run on modern/usual windows platforms
+feat_os_windows = [
+  "feat_Tier1", ## == "feat_os_windows_legacy" + "hostname"
+  ]
+## (secondary platforms) feature sets
+# "feat_os_unix_gnueabihf" == set of utilities which can be built/run on the "arm-unknown-linux-gnueabihf" target (ARMv6 Linux [hardfloat])
+feat_os_unix_gnueabihf = [
+  "feat_Tier1",
+  #
+  "feat_require_unix",
+  "feat_require_unix_utmpx",
+]
+# "feat_os_unix_musl" == set of utilities which can be built/run on targets binding to the "musl" library (ref: <https://musl.libc.org/about.html>)
+feat_os_unix_musl = [
+  "feat_Tier1",
+  #
+  "feat_require_unix",
+]
+## feature sets with requirements (restricting cross-platform availability)
+#
+# ** NOTE: these `feat_require_...` sets should be minimized as much as possible to encourage cross-platform availability of utilities
+#
+# "feat_require_crate_cpp" == set of utilities requiring the `cpp` crate (which fail to compile on several platforms; as of 2020-04-23)
+feat_require_crate_cpp = [
+  "stdbuf",
+]
+# "feat_require_unix" == set of utilities requiring support which is only available on unix platforms (as of 2020-04-23)
+feat_require_unix = [
+  "chgrp",
+  "chmod",
+  "chown",
+  "chroot",
+  "du",
+  "groups",
+  "hostid",
+  "id",
+  "install",
+  "kill",
+  "logname",
+  "mkfifo",
+  "mknod",
+  "nice",
+  "numfmt",
+  "nohup",
+  "pathchk",
+  "stat",
+  "timeout",
+  "tty",
+  "uname",
+  "unlink",
+]
+# "feat_require_unix_utmpx" == set of utilites requiring unix utmp/utmpx support
+# * ref: <https://wiki.musl-libc.org/faq.html#Q:-Why-is-the-utmp/wtmp-functionality-only-implemented-as-stubs?>
+feat_require_unix_utmpx = [
+  "pinky",
+  "uptime",
+  "users",
+  "who",
+]
+## (alternate/newer/smaller platforms) feature sets
+# "feat_os_unix_fuchsia" == set of utilities which can be built/run on the "Fuschia" OS (refs: <https://fuchsia.dev>; <https://en.wikipedia.org/wiki/Google_Fuchsia>)
+feat_os_unix_fuchsia = [
+  "feat_common_core",
+  #
+  "feat_require_crate_cpp",
+  #
+  "chgrp",
+  "chmod",
+  "chown",
+  "du",
+  "groups",
+  "hostid",
+  "install",
+  "logname",
+  "mkfifo",
+  "mknod",
+  "nice",
+  "pathchk",
+  "tty",
+  "uname",
+  "unlink",
+]
+# "feat_os_unix_redox" == set of utilities which can be built/run on "Redox OS" (refs: <https://www.redox-os.org>; <https://en.wikipedia.org/wiki/Redox_(operating_system)>)
+feat_os_unix_redox = [
+  "feat_common_core",
+  #
+  "uname",
+  "chmod",
+  "install",
+]
+# "feat_os_windows_legacy" == slightly restricted set of utilities which can be built/run on early windows platforms (eg, "WinXP")
+feat_os_windows_legacy = [
+  "feat_common_core",
+  #
+  "arch",
+  "nproc",
+  "sync",
+  "touch",
+  "whoami",
+]
 
 [workspace]