Signing 100 extra transactions would only require an additional 6400 bytes, which can be easily transferred even with a slow 100KB/s connection in just 64ms. In this case, latency will still dominate.

RBF (Replace-By-Fee) has a minimum incremental relay fee of 1sat/vByte by default. By using 100 pre-signed transaction variants to sign every possible minimum incremental relay, a range of 1sat/vByte to 100sat/vByte is covered. This range is believed to be sufficient for getting the transactions mined in any block throughout Bitcoin's entire modern history.

On the other hand, CPFP (Child-Pays-for-Parent) requires two transactions and thus extra bytes. Unless there are edge cases involving very large transactions in low-fee environments, CPFP is not superior to RBF.

For more information, you can visit Peter Todd's website at https://petertodd.org or contact him via email at 'peter'[:-1]@petertodd.org.