Your idea is not worthless and is already used in one of the altcoins.
Out of curiosity, which altcoins?
The only requirements are to wait long enough between beginning and committing a transaction and to not reuse addresses (private keys).
What about the added requirement of a good CSPRNG source for
every tx (not required by ECDSA), something which is more difficult to obtain in an isolated IoT environment w/o added (and unauditable) hardware support?
There's also extra non-volatile state which much be maintained to commit the tx, another weak suit of IoT devices in general, correct?
ECDSA isn't
that hard, otherwise hardware wallets wouldn't exist....