List of overlapping/intersecting features for "replace terrain points"

Hi all,

I hate to bother you, but after several days of fruitless efforts to find a solution I thought I'd just ask if anyone knows if what I want to do is possible.

So I have this Terrain-Dataset containing around 500 Multipoint feature-classes. Every other month or so I'm going to get updates for some areas that randomly overlap some feature-classes. My plan was to use "replace Terrain points" to update the terrain. This tool needs as input:
-the feature-class in which points need to be replaced
-the feature-class with which to replace them
-(optionally) a clipping polygon

What I wanted to do was:
-check which Multipoint feature-classes in the Terrain need to have a part of their points replaced
-output these as a list of feature-classes
-iterate over this list in the model-builder to run "replace Terrain points" for all new feature-classes

My efforts were already foiled by the first step. So my questions at the moment are:

Is there a way to determine which feature-classes have common areas and output a list of filenames/feature-class names to use as a basis for further processing?
Is there an obvious easier way I fail to see?

My current approach (which I hope will get the work done but is unsatisfying on an intellectual level) is to create a single feature-class containing all the points of the original terrain, create a new terrain and then run the replace tool for that new terrain.

Thanks for reading and (in advance) for responding!

Yours,
B. Reiter