Thanks a bunch!
It is working now.
This new notation is a great improvement to the exporter. (I didn't get how to note each frame, because "," caused an error message. Probably in the py script was an instruction, but I wasn't aware of that, until now.)
I had to remove the old exporters from my blender folder first to get access to this one, though.

Ventilator :
Even if you do animation by hand you can make it loop well,
Just copy the first frame animation to the end of your sequence to make it loop well (with some touches perhaps) !

Some games like Guild Wars, use simple baked animations and it works well.
You have to manually retouch animations sequence to avoid jerks. And they use several animation of clothes with blending ;
like idle, walk , run, jump etc ... !
It's fake, but looks really good, specially if the animation use bones and if you have done some code modifying slightly the animation by orientating clothes depending on character direction and speed.

You probably have to set several walk cycles after another, and then take the baked physics from a later cycle to get results where the animation is quite close in the beginning and in the end of that cycle.
When you use one cycle only, then the baked physics just starts at the beginning to that cycle, what is very different to its movement within a row of walk cycles.

I want to use the second half of a baked physics animation, because that looks as if I can adjust it with very few effort to get a cycling animation.

Wouldn't it be nice if there was a "make seamless" function which lets you define the start/end frames in a cycle and it attempts to smoothen the transition from the end into the beginning.

Jibb

In MED you can create interpolated frames, but only one by one.
You have to copy the first frame to the end of the animation, because it doesn't interpolate between the first and the last, but only between one frame and its follower.

This is the result of my tests, nothing exciting, just a slightly moving 'carpet' or 'curtain'.
cloth.mdl
cloth_physics.blend

maybe it would be possible to write a script for that. which fades the last few frames of the previous cycle to the last few frames of the cycle you want to export. i am not sure how convincing this would look physically though.

I am wondering that as well. It could look like a rewind animation. It depends on the situation.

It depends on the frames that you choose to 'merge'. If they move in a similar way, so to say in the 'same direction' - then it should work.
Other than that, it might be a good decision to use more than one cycle for the baked physics, because the mere repetition could look unnatural.