About "No registration" and "Custom Field"

I have created several custom fields and select no-registration under configuration>checkout>registration

I find that for visitor who has made a purchase, Hikashop will has a user record that stores his email and custom fields. Later on when the visitor wants to register (e.g. to manage his account, on Joomla), as long as he use the same email address, no duplicated Hikashop-user record will be created. That's great!

Now the problem is, if the visitor register thru Joomla first, all customer fields will be blank because they are not on Joomla's form. How can I lead him to answer those custom fields created in Hikashop?

(I have tried the "Redirect Joomla registration to HikaShop Plugin". As no-registration is selected, custom fields are answered but no account is created on Joomla.)

Thanks

oic
My contingency is to use "no account activation" (on Joomla) + "simplified registration" + captcha to replace "no registration"
Hope can work that out.


About the future version

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One of the current "limitation" is in fact a benefit. I mean visitor can input once and only once the hikashop custom field, during registration but not later. Otherwise, greedy people can get a lot of birthday gift if they keep on changing their birthday record when they want. So, suggest to add a control flag on custom field panel to control whether visitor can "re-edit" the value.