While the "Send Later" feature is very useful, it can be vastly improved and I do not believe the changes I am about to suggest would be difficult at all. Currently, if someone wants to schedule an email for later, they have to compose it first, which is fine, but then they have to remember to click the arrow next to the orange "Send" button to reveal "Send Later." When one has been sending emails all day, it is very easy to accidentally just hit the "Send" button instead which results in the major transgression of inadvertently sending a second email, back-to-back, to the contact. This can all be solved by providing two options: Keep the lower left orange "Send" button, but on the lower right side of the window create a "Send Later" button that is a different color. Clicking that button will have the same affect as clicking "Send Later" in the current configuration but will all but eliminate the potential for error.
I like the idea of moving the send later option out from under the arrow, but I would like to see them side by side rather than on opposite sides of the email. I think it could still be easily overlooked.