EDIT: SCALE is the most important thing to sort out.
Dickering of over the “export” format is going to create a library of mess. Each model should have the source program’s native file format, a bunch of exports of different filetypes and any textures in a non-proprietary format. A REAME is also a good requirement: It could have a boilerplate that could be used to generate a library “listing”. The README should list the version of the source program. The README should list the scale (eg. 1" X1000)
EDIT: I have converted a LOT of models (literally 1000’s) from all kinds of sources. You do not want to clean a model in some crappy format. Getting the source files is your best bet to having something useable. As a couple of people have pointed out, most formats have versions that had compatibility issues, which is why I suggest having a number of options. Compounding the format choice is the exporter implementation in any given source package. It all adds up to more is better in the case of exported models.