OPnet.org can do everything Citrea.xyz wants to do
Citrea can already do everything they want to do with no changes made to Bitcoin Core or anyone else.
The thing that kicked off all of this drama is that a Core dev read Citrea's whitepaper, saw the construction that they were going to use, and said "wow that's dumb, you can do better if the OP_RETURN limit was higher". The whole point is that the current construction would insert 2 unspendable outputs into the UTXO set and they were doing this in order to work around the OP_RETURN limit.
with no BIP(?)
There isn't a BIP; this isn't a BIP-able change.