Another strategy might be to try for SkyTeam Elite status if you're close, presumably on CZ since that's where your redeemable miles are, but largely fly the best schedule and cheapest ticket for you. You already have Diners Club lounges.

For additional lounges, think about a DL SkyClub membership, but this is expensive if you're not a DL elite, although the DL Chinese website might offer cheaper memberships for nonUSA residents.

If you have Diners Club, you might be able to get an AmEx Plat card, which is good for DL lounges when flying DL, AA lounges when flying AA, and US lounges anytime. This would cover very nice lounges in NRT when you are connecting there to/from a DL flight.

A cheaper alternative is to take a Priority Pass membership; the cheapest is under $150 per year but charges about $30 for every lounge visit. There are a bunch of PP lounges in China, including IIRC some CZ lounges, but AFAIK no Wuhan lounge is on the list.