This is an issue I've run into a few times lately, as fares have risen, as award availability has declined a little, and as AA has offered more paid fares where a roundtrip costs less than the two one-ways booked separately.

Right now, there's a roundtrip I'm trying to book. The paid fare is high enough to warrant using miles, but there are no saver level award seats for my return. Ideally, I'd use miles for the outbound and pay for the return. But the paid return, when booked as a one-way, costs almost as much as the full paid roundtrip would.

So I can pay the too-high price for the whole trip, or use an anytime award for the return, or take another airline for the return.

AA already lets you mix classes/cabins on a roundtrip, whether paid or award. I'd love to see them go a step further and let you mix paid and award. Besides addressing the OP (and my) situation, this might also solve another frequent complaint here: elite and companion traveling together, one on paid and one award, so separate PNRs, and the companion loses the elite-companion benefits like free checked bags.

One suggestion for the OP, if their situation matches mine. If you'll be revisiting the destination at some point in the near future, consider making the paid one-way into half of a roundtrip. For example, for this trip fly HOME-XXX as a one way award. Then buy XXX-HOME and (months later) HOME-XXX as a paid ticket, satisfying the roundtrip purchase requirement, and finally XXX-HOME on an award (hopefully award space available).