@animagic
Yes! I've already done that. I have purchased some CC clothing from the Marketplace that didn't live up to my standards and did just that. The simple process was to export the item as an .obj  file in the exact pose that you have at the beginning of your animation. Export your character with animation via the Alembic option in iClone with footwear, but without any other clothing. Import your character as an Alembic file. Import the .obj file via the (Add) obj to garment located in the MD menu on the left hand side. Simulate and enjoy! First time, every time!

No weight mapping, guess work, poke through, Photoshop, etc. However, I won't go through the step by step hassle of what it takes to get it back to iClone. It's a 1 to 4 frames at a time process which takes me 6 hours for a 15 second animation!! Very soon, I will be able to import my Alembic files back into iClone within  matter of seconds! Until then, I have to gear up for at least a 6 hour session in iClone, or use another program. I mostly design my own clothing, but as I mentioned earlier I bring in some wonderful dForce clothing that I purchased in DAZ and use MD  for the simulation part. I just didn't layout the details. It's the same process. I'm only using very few items that I purchased from DAZ or the Marketplace and only for personal use as I'm not selling anything. I hope that leaves me legally in the clear!... and I hope that long winded rant helps to answer your question.

@MINI3D: Yes that is clear. I will wait for official support of Alembic import as I currently don't have MD anyway.

If it works as expected it will be worth it. I suppose the clothing needs to have an export license?

---

Yes.

Apparently I do have OBJ to Garment option in MD . I can't wait to start playing with it!

And you guys do not need an export license for cloth if you export from CC as OBJ with current pose.
Then just extra step for separating and saving particular cloth through Blender.

That's good to know.! I'm just so used to getting it because I'm all over the place with my programs that I export to, and without the export possibility I get the message that tells me that I didn't purchase the export version. So it's kind of automatic for me now. Thanks for finding a workaround. I'm too far down the rabbit hole to take advantage of it now, but I'm sure that it will help others.

Sure thing
And I forgot about another easier option. There is not need for Blender at all. Just bring OBJ exported from CC directly to iClone selecting option to separate.
Then delete unnecessary stuff (like avatar mesh... etc). There is a slight offset by Y, which can be easily tweaked.

Indeed!

Many thanks for your video!! I highly appreciate your help!!

You are welcome

Now looking into the future (new automated alembic import) and trying to see if importing external garments from OBJ into MD is really a viable option, I came to the conclusion, that it is not.
This feature is highly underdeveloped so to speak.

You can apparently bring the OBJ as garment without UV tracing with no problem. But then there is no materials separation and no patterns of course.
So you may not assign different fabric and physics to parts of the garment.

UV Tracing on the other hand, is totally useless (at least for a few closing items I was trying to import). Algorithm is not smart at all.
A small UV inconsistency in joining parts and imports fails, or only parts of the mesh is imported.
Even after fixing UVs, some parts of the mesh does not show up after import (although no error is displayed anymore).
Importing missing parts separately, again does not offer the option to convert to pattern so that is can be stitched to the rest of the imported garment.

Another problem is, that resulted UV does not follow original texture at all. You have to spend quite some time editing UV in MD to match the texture.
And that is such a simple thing to automate. As I said - quite underdeveloped.

Maybe with some luck something can be eventually imported successfully, but I tried DAZ medium to high complexity cloths and it mostly failed.

PS I'd be glad if someone proficient in MD gives some pointers.