Would making 'this' a reference rather than a pointer be better in retrospect?

Answer 1

References didn't exist in the language when this was created.

Answer 2

From Bjarne Stroustrup's "The Design and Evolution of C++", Addison-Wesley, 1994, pp 39-40:

Sometimes, people ask why this is a pointer rather than a reference and why it is called this rather than self. When this was introduced into C with Classes, the language didn't have references, and C++ borrows its terminology from Simula rather than Smalltalk.