Digital purchases as email attachment?

Is it possible to have purchased digital items delivered as an email attachment instead of a link?
We'd like to keep guest checkout because it increases sales, but I understand it's not possible for security reasons.
Is it possible to turn on registration product by product?
Is there any way around forcing everyone to register so that some people can purchase digital items?

(This is for Hikashop Business.)

Hi,

Unfortunately, none of these are possible for now. Registration is required for digital products sale and you can't turn it on on a per-product basis.