Hi,
Sorry but I'm still not clear on everything and I don't agree on everything you said either. Nevertheless, I'm happy to discuss the matter.
B. I agree with that. However, I didn't know that Joomla provides the necessary triggers to add elements to the Joomla profile page or the backend user form. And I'm still not clear on whether that's the case, or how it would be possible to display the fields elsewhere on the page, etc.
It seems that you're saying this is possible but I don't know how and for the backend profile edition page I can indeed see in your screenshot that they are able to add tabs there. I don't know how they are doing it so I can't say if it could be done for HikaShop too.
C. Adding a HikaShop tab to the backend user account edit form is an interesting idea. I however don't know how that is possible.
Regarding the frontend, I'm not clear on what is possible so I can't say much. I guess checking the code of these plugins would help in understanding what's possible and how to do it.
D. Again, I don't know of any way to add data to the joomla frontend profile page. You're saying it as if creating a plugin of the group "user" would be the solution, but that's not the problem here. A plugin of the group "system" has the same access to events than plugins of the group "user". If I knew how to add tabs on the joomla backend profile page, I could do it from the system plugin if I wanted.
Finally, the frontend Joomla profile page is quite cramped and not suited to display all the data available with the many views of the user control panel. On the other end, if other components add their stuff to the joomla profile edition page, then if you give the customer access to the HikaShop user control panel, he will have access to the Joomla profile (and thus the other components stuff) as well as all the other things HikaShop provides. Without even talking about the technicalities of how to do it, as a practical thing, I don't feel that the orders listing, the address listing, the downloads listing, the affiliate program, the HikaSerial "serials" area, the HikaSubscription "subscriptions" area, etc could all fit inside the Joomla profile page. To me, it make sense that there is a central control panel for the user on an ecommerce website, which also allow the user to access his profile, and that's what we already do.