You could have a timelocked transaction that has a zero value input (and
other non-zero inputs).  If the SF happened, that transaction would become
unspendable.

The keys to the outputs may be lost or the co-signer may refuse to
cooperate.

There seems to be some objections to long term timelocked transactions.

If someone asked me about it, I would recommend that any timelocked
transactions should very carefully make sure that they use forms that are
popular.

I think the fairest rule would be that any change which makes some
transactions invalid should be opt-in and only apply to new transaction
version numbers.

If you create a timelocked transactions with an undefined version number,
then you have little to complain about.

If the version number is defined and in-use, then transactions should not
suddenly lose validity.

A refusal to commit to that makes long term locktime use much more risky.

On Thu, Sep 7, 2017 at 12:54 AM, CryptAxe via bitcoin-dev <
bitcoin-dev@lists.linuxfoundation.org> wrote:

> As long as an unspendable outputs (OP_RETURN outputs for example) with
> amount=0 are still allowed I don't see it being an issue for anything.
>
> On Sep 5, 2017 2:52 PM, "Jorge Timón via bitcoin-dev" <bitcoin-dev@lists.
> linuxfoundation.org> wrote:
>
>> This is not a priority, not very important either.
>> Right now it is possible to create 0-value outputs that are spendable
>> and thus stay in the utxo (potentially forever). Requiring at least 1
>> satoshi per output doesn't really do much against a spam attack to the
>> utxo, but I think it would be slightly better than the current
>> situation.
>>
>> Is there any reason or use case to keep allowing spendable outputs
>> with null amounts in them?
>>
>> If not, I'm happy to create a BIP with its code, this should be simple.
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>>
>
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