AJ winning the rumble could work if executed well. Granted that's a very big "could" and "if."
One of the few things TNA did right early on was establishing AJ as a guy to watch. One of my favorite matches is the double elimination four way to crown the first X division champion. The story of the match was all about making AJ. He starts off strong, giving Low Ki and Psicosis their first eliminations, only for the fresh Jerry Lynn to give AJ his own first elimination. Lynn dominates the rest of the match until it's down to him and AJ, and AJ has to beat him twice in a row to win.
If AJ were to win the Rumble, the best way to go about it would be to give him something similar the Flair '92 treatment. Have him enter relatively early (3-6), make a strong first impression. He doesn't need to dominate, but have enough stand out spots spaced out during the middle portion. As it gets down to the heavy hitters in the final ten or less, have him hold his own and look like he belongs. Even if he doesn't win and just makes it to the final four or three, that's still at least 30-40 minutes of ring time. Plenty of time to introduce and establish him for a potential big WM match. Provided his elimination isn't ultra lame.