Possible FUE results of Norwood 6 based on a bit of simple maths, a little over harvesting and some mdp on the sides?

Even if your math is right, the scarring from 10,000 FUE grafts would be more noticeable than scarring from a Strip surgery.  In the real world, hairs around the neck and over the ears and are not always considered good donor hair.  In addition, a portion of the 10,000 FUE grafts may be transected (5 to 10%) and the ones that are not transected may not all take.  In the real world, 100% of implanted hairs do NOT all grow.  Finally, there will be significant FUE scarring and you would need SMP to help disguise it.  We've seen many FUE patients from all over the world who were left with very patchy scars.

Your best bet is to just go in for a consultation. There's too many outside factors, like hair density, color, thickness, graft survival rate, etc. that can affect how many grafts you have available and how many you would need to achieve the results you want. It's important to have realistic expectations and expecting to be able to get back a full head of hair as a norwood 6 is aiming awfully high, but whether or not it's possible a doctor couldn't say without seeing you in person.

You may be able to harvest 5000-6000 grafts, donor providing, throughout your lifetime, however if you are a class 6 that will likely not provide a full head of hair.  It will however make a significant impact in your appearance.  I recommend concentrating the grafts front and top and then lastly crown to my patients.

Your math is partly right. The donor area is always determined on the Class 7 scale not the Class 6 scale, which essentially reduces the donor area to about 20,000 hairs or 10,000 grafts, which can be harvested at say 60% assuming that you have an average donor density.  Graft numbers are adjusted according to hair weight (coarse vs fine), color and contract between hair and scalp and hair character.  The artistic judgment of the surgeon manages the multi-variant analysis as everything is not by the numbers alone.