@Enzojz : I think that @Grimes was more thinking of something to put in the 3d file that will define the coordinate of the seat and write them in the mdl file when converting. Like you can create custom object in Blender that define lod or grp for the exporter plugin.
It's already possible to do that with a function in the mdl file, although i tend to only use variable as the spacing between seats is often irregular (i have attached an example). The thing is, it's tedious as we need to go into the 3d app (blender in my case), and manually check the coordinate of every seats.