This being said, there are some caveats.
Some apps use kernel extensions. 32bit kernel extensions don't load into the 64bit AIX kernel. Either change to 32bit AIX kernel or get an updated kernel extension from the app vendor.
Tweaking the AIX kernel down to 32 has some drawbacks though. E.g. JFS2 and 32bit AIX kernel are no good match. But you can always install an AIX 32bit with plain JFS if necessary.
Sometimes an app will fail to load&run into an environment that it doesn't know about, so even if that env is perfectly valid, the app will fail to start.
Bottom line: try out your app and see how it goes.
HTH,
p5wizard