Can white gesso be diluted to make it translucent?
A single layer of white gesso will likely show the underdrawing through. I thin my gesso for easier application and usually do three or more coats to get a good solid base. However, you would be using less gesso to keep it translucent, so the canvas may get less of the protection the gesso provides.

You could use acrylic medium to seal the canvas, essentially it would be like using gesso binder without the pigment. Go with matte medium since gloss will change the look of the canvas and top layers may not adhere as well. 

You could also use rabbit skin glue as a base coat, it is clear and will seal the canvas. Traditionally this would be the first covering on the canvas before applying gesso or under painting. It comes as dry granules that you mix with water and cook a little before applying, so its a little more complicated but it will do the best job at providing an archival clear protective coat to the canvas for what ever you want to put over it, oils or acrylics.