Yes, CX will let you check in with the MP GO rules, no problem.

Coming back should also be the same -- AA gives OW members the same allowances that their own members get. If the check in agent gives you any hassle ask for a supervisor to clear it. If that doesn't work, then you can argue the MSC rule and get them to approve it that way. You might need to show them the CX website where it says what MP GO members get. If you are worried about the return trip, print out that page in advance and show it to the AA agent.

I do this all the time as an MP GO and I've never had a problem with 3x 32kg pieces in either direction.