I agree, some good date-object like functions would be great.
For example, in Vim Mode, if you use ctrl-a or ctrl-x you can increment or deincrement a number. It would be nice to be able to do the same with a date that matches your Daily Notes format. Or do date-math operations based on the current date, or a specified date.
Are you already familiar with the discussions about Expanso, where people are using snippets to create your specific example of a Tomorrow and Yesterday link? Fun with espanso