How can I edit received emails in Apple's Mail app? Also, delayed sending of replies?

Question

I finally switched to Apple's Mail app 4 months ago after 12 years of using Eudora (because of the inevitable - that Lion or Mountain Lion, when I upgrade, will not support the foundation architecture that Eudora is built on).
There are (AT LEAST) two functions available in Eudora that I very much want to do with Mail and currently cannot figure out how to do. I'm hoping that someone knows of a plugin that will do these functions, or will write such a plugin, or will tell me how to make this suggestion to Apple to include in a future update.
1) I want the freedom to EDIT a received message - to correct a subject line, or make it more relevant for my reference, or add a key word/prefix to the subject for future searching and archiving, along with being able to edit the message itself, so that it is the equivalent in a book (or an eBook) of adding comments/marginalia for future reference. (In my opinion, once I receive an email message, it is MINE - so I should be able to do what I want with it (which includes the responsibility of not rewriting a message to resend to appear as deceptive or fraudulent).
2) Write up a draft email, that would reside in the "Send" folder of Eudora, and for which I could select a time in the future that it should be mailed (dependent on the fact that Eudora would be running at that time, else it would send the next time Eudora was opened. I would LOVE to be able to do that in Apple Mail. Rationale: Often, when I receive an actionable email, I want to respond at that moment while the subject is fresh, but due to priorities or scheduling reasons, I don't want the response to go out just then. Maybe I want the response to go out after an event three days from now, but I want to process the message right now, and I don't want to have to remember to make a ToDo item to remind me in 3 days.

Answer 1

Thanks, a brody.
That tip takes me further down the field. And, I am able to do stuff like indent and change font color of my comments which is very helpful.
However, the big disappointment is that by dragging the original message to the Draft mailbox and then back to the original one after the edits is that it removes the original sender's name and puts mine in along with changing the heading info on date and time. That is, it creates a new message, rather than allowing me to modify the original one to suit my needs.
All the same, this was a very helpful tip. Thanks again.
Anyone know of a plugin?..............or two?....