User selection of text elements within mail forms

Hi experts

we have a business requirement to allow business users to freely choose text elements when composing a mail in the IC. A text element pretty much represents a paragraph of pre-written text.

What the business wants is that the "mail form" is merely a framework of the mail, and then the user can compile the text very customer request-specific based on predefined texts.

Moreover, as the business today uses 100+ of those predefined paragraphs, those need to be structured "nicely" (e.g. hierarchical structure).

Any experience with this or a similar requirement? How can it be fulfilled?

Thanks in advance!
Christian