Great stuff... looks like it's certainly a good alternative.
A mix of resolutions is good for reducing memory usage, but if you have the RAM, disk space and data then you might as well make the entire terrain as high a resolution as possible as the final TER file size will still be the same. My old workflow of creating geotiffs in GlobalMapper (v4.7) and then converting these to TERs using 3DEMs could also be done with Microdem.
The only problem I had was with 3DEM. I was using UTM projection to allow for easy tiling of TER files and creating different resolution TERs. When I got to my larger, low res terrains I eventually ran into problems when the coordinates were too far out of the range handled by 3DEM (e.g. very large negative coordinates for terrains spreading across more than one UTM zone)
My Swiss Alps terrain set was the first one to highlight this problem. I had to use a UTM zone closer to the western edge of the Alps in order to be able to extend the terrain to include the UK. With a direct export to TER (of any size) from the new version of Globalmapper that problem went away. I also found the final TERs were a bit cleaner without the intermediate conversion step but this is certainly a pretty good (free) alternative.