c) A blockchain where we allow monetary transfers to be recorded on and reject malicious transactions trying to abuse it as cloud storage. Like when we reject any transaction containing more than 1 OP_RETURN output (for many years).
And what's the border to that? Alright, softfork says that more than 1 OP_RETURN is invalid. Great. Now, people don't use OP_RETURN at all. They store their data in chunks of 160-bit addresses, and send 0 coins to multiple of these addresses. What next? Invalidate transactions which spend 0 coins? Alright, they then spend 1 sat for each. You've probably guessed how this goes. At some point, they become indistinguishable from regular transactions.
There's difference between invalid and non-standard. IIRC transaction with more than 1 OP_RETURN and OP_RETURN with more than 80 bytes of data are deemed as non-standard. So rather than soft-fork to make future Ordinal TX invalid, changing default behavior of full node software to consider most/all Ordinal TX as non-standard would be less invasive option.