Arriving here to add my strong vote to this feature. Our HubSpot traffic have 0% SPF alignment, unlike other providers (MS, SendGrid, Freshdesk) we use that have 95-100%. Initially, I thought we were doing something wrong in our SPF configuration setup for HubSpot marketing email. After a long conversation with HubSpot Support it became clear that it is the lack of support for aliasing the “Mail From” that prevent HubSpot email to be SPF aligned.
As others have stated in this thread, and as other providers have done, this is clearly possible to implement.
It is disheartening to see that this idea have been promoted here a long time ago, yet without any attention from HubSpot.