Rincewind, you can export directly from blender to mdl7 with the help of ventilator's plugin.
I needed some time to find the link to its latest version. Its here:

http://user.schule.at/go/export_gs_mdl7.py

You have to copy it into the following folder where you installed blender, for instance:

...\Blender Foundation\Blender\.blender\scripts

Before you export your model you have to select it, if it consists of different objects, you have to select all the objects that are part of that model (RMB + Shift).