There isn't any way currently to apply different settings to different faces. Eventually I would like to figure out some way to do this, but there are some things that are a bit complex, like making sure that faces that share edges have a common structure along their shared edge.

If you have a larger face that you want to subdivide, then that's what the Divide Larger Than setting is meant for, check out this older post that has some info on the mesh settings: http://moi3d.com/forum/index.php?webtag=MOI&msg=236.1
There is an example there that shows how you can divide a larger surface that has kind of shallow curvature in it:

The number you put in there is a distance. If a polygon edge is larger than that distance then the polygon will get subdivided. You can also control whether this additional subdivision will be applied to only curved surfaces leaving totally flat planar surfaces alone, or whether to only apply to planes, or all surfaces.

So you need to know the size of your face - you can use the grid to gauge this or also draw a line snapped on to the edges of the face and watch the distance of the line which shows up in the bottom toolbar in the "d" box under the x,y,z coordinate readout.

Once you know the size of your face, put in some fraction of that in that "Divide larger than" box. Like for instance if your face is about 4 units in size across, you can put in 1 in there which will force 4 extra divisions to happen on it.

Let me know if you need additional explanation, you can also e-mail me pictures or model files at moi@moi3d.com and I will keep those private.

- Michael