I would suggest Adobe’s built-in Adobe ExtendScript language that was added to Photoshop 7 and later. This is an extension to the javascript language that currently allows you to automate Adobe After Effects, Audition, Bridge, Encore, Illustrator, Photoshop and Premiere. Unlike Actions in Photoshop, the javascript/ExtendScript combination allows you to make a truly professional user interface for your import tool, with dialogs, warnings, prompts, drop down lists, text entry, etc.
You can pretty easily export your 3D passes/elements to separate image files via Maxscript or the 3ds Max UI, then have your ExtendScript-based tool import/arrange/name them as layers/groups in a PSD (or in an After Effects composition).
Be warned that the ExtendScript docs assume that you either know or can figure out basic javascript on your own, as they focus on the Adobe extensions of javascript. Learning the basics will involve a lot more google searches than Maxscript, which has comprehensive docs in one place.
However, doing this through ExtendScript will be worth it if automating the PSD structure is the real challenge you want to overcome…