So as long as the chain of online code-shares is unbroken, conceivably (though very difficult in practice), could one daisy-chain together a RTW that used exclusively AA flights and AA codeshares for (nearly) the entire route. For example:

CPT-LHR (AA operated by BA)
LHR-HEL (AA operated by AY)
HEL-CDG (AA operated by AY)
CDG-KUL (AA operated by MH)
KUL-BKK (AA operated by MH)
BKK-HKG (AA operated by CX)
HKG-CGK (AA operated by CX)
CGK-NRT (AA operated by JL)
NRT-ORD (AA operated by JL)
ORD-DOH (AA operated by QR)
DOH-NBO (QR operated by QR - though I'd thought this codeshare also once existed)