If you are willing to do SSLv3 the POODLE attack downgrades you and steals one byte of encrypted data per 256 iterations.
If you demand SCSV to defend against this downgrade, every implementation that speaks SCSV also offers a better protocol version than SSLv3 so you won't end up talking SSLv3 anyway, thus you should just not implement SSLv3.
You also shouldn't implement RC4 in 2019. Refuse to connect to peers that only offer RC4 instead.
TLS version can usually be upgraded transparently by, say, web hosts. To retrofit CORS you actually need to inspect legacy code and sometimes make modifications (in addition to modifying say nginx config), which is a fair bit harder.
Then again, only with TLS 1.3 do we get rid of RC4!! Except when downgrading to 1.2, 1.1, 1.0, ssl3 (is that even around?)