If my idea is worthless, then it strengthens the point why ECDSA is needed, and people will apreciate ECDSA more.
Your idea is not worthless and is already used in one of the altcoins. It's actually a nice solution for IoT-friendly cryptography for which ECDSA is too "heavy". The only requirements are to wait long enough between beginning and committing a transaction and to not reuse addresses (private keys).
Or you could use Winternitz (Lamport signatures) with Merkel trees for a more robust solution that doesn't reveal the private key and has roughly 1/20th the resource overhead (not including hardware acceleration of SHA256) of the most efficient (curve25519) elliptic curve cryptography (not factoring in batch mode). But the major downside is the size of signatures increase exponentially with increasing bit security level, which is also the problem with RSA. The theoretical gain is future quantum computing resistance, but research is proceeding on elliptic curve (isogenies) variants which are quantum computing secure.
Yes. It looks like OP is suggesting a Lamport Signature coin. Go and build it please
